Showing papers on "Propylthiouracil published in 1983"
TL;DR: It is reported here that both noradrenaline and cold exposure increase BAT 5′D-II through α1-adrenergic receptors, whereas depletion of catecholamines with α-methyl-p-tyrosine (MPT) prevents the effect of cold but not that of nor adrenaline.
Abstract: There are several mechanisms by which homeothermic animals increase heat production, including shivering, sympathetic nervous system activation and stimulation of thyroid hormone secretion. Studies in rats have shown that increased sympathetic activity causes increased heat production in brown adipose tissue (BAT) after cold exposure or food ingestion1–3. Acute cold exposure also increases circulating thyroid hormones4 which in turn stimulate cellular metabolism through induction5 of various enzymes. Most metabolic effects of thyroxine (T4) are thought to be due to the triiodothyronine (T3) which is produced from T4 by a process of 5′ monodeiodination. There are two enzymes responsible for this reaction6–8: type I, or propylthiouracil (PTU)-sensitive iodothyronine deiodinase (5′D-I), which is reduced in hypothyroidism, stimulated in hyperthyroidism and probably provides most of the circulating T3 in the adult rat9. Type II 5′-deiodinase (5′D-II) is characteristic of brain and pituitary, is increased by thyroidectomy, is not inhibited by PTU and provides 50–80% of the intraceUular T3 in these two tissues. Recently, 5′D-II activity was identified in interscapular BAT10. As the sympathetic nervous system influences the metabolic activation of BAT, we have studied the effects of noradrenaline and acute cold exposure on BAT 5′D-II. We report here that both noradrenaline and cold exposure increase BAT 5′D-II through α1-adrenergic receptors, whereas depletion of catecholamines with α-methyl-p-tyrosine (MPT) prevents the effect of cold but not that of noradrenaline. These results suggest that the sympathetic nervous system may increase T3 production in rats by stimulating BAT 5′D-II. By increasing metabolic rate, this rise in T3 would enhance the thermogenic response to sympathetic stimulation.
375 citations
TL;DR: The data suggest that antithyroid drugs should be administered cautiously to patients over age 40, and low-dose methimazole therapy may be safer than high-dose therapy or treatment with conventional doses of propylthiouracil.
Abstract: The records of all patients with antithyroid drug-related agranulocytosis at two Boston hospitals (Group 1, 14 patients), as well as the published case reports of 36 patients with this syndrome (Group 2) were reviewed. The clinical characteristics of these patients were then compared with those of 50 hyperthyroid patients who had taken antithyroid medication without untoward hematologic reactions (Group 3). The mean ages of patients in Group 1 and Group 2 were significantly greater than that of Group 3 (50.6 +/- 16 years versus 35.7 +/- 13.7 years, p less than 0.001; 46.3 +/- 18.7 years versus 35.7 +/-- 13.7 years, p less than 0.02). By chi-square analysis, the relative risk of developing agranulocytosis in patients over age 40 was 6.4 times that among younger patients (p less than 0.001). The mean doses of methimazole in Group 1 and Group 2 were significantly higher than that in Group 3 (43.8 +/- 9.9 mg/d versus 29.5 +/- 10.4 mg/d, p less than 0.001; 40.7 +/- 15.7 mg/d versus 29.5 +/- 10.4 mg/d, p less than 0.02), with and 8.6-fold increased risk of agranulocytosis with doses greater than 40 mg/d (p less than 0.01). In contrast, the mean doses of propylthiouracil did not differ among the three groups. These data suggest that antithyroid drugs should be administered cautiously to patients over age 40. Because no cases of agranulocytosis were seen with methimazole doses less than 30 mg/d, low-dose methimazole therapy may be safer than high-dose therapy or treatment with conventional doses of propylthiouracil.
205 citations
TL;DR: Data show that rat pituitary tissue contains two distinct iodothyronine 5'-deiodinating pathways that differ with respect to substrate specificity, PTU sensitivity, reaction kinetics, and regulation by thyroid hormone.
Abstract: We have studied 5'-deiodination of thyroxine (T(4)) and 3,3',5'-triiodothyronine (rT(3)) in rat pituitary tissue in vitro, with respect to substrate specificity, reaction kinetics, effects of 6-n-propyl-2-thiouracil (PTU), and the time course of effects of thyroid hormone depletion and repletion. Removal of one phenolic iodine or both tyrosyl iodines from the T(4) molecule resulted in compounds that were not deiodinated, but alterations in the alanine side chain had little effect.5'-Deiodination of 2 nM rT(3) by pituitary microsomes from euthyroid rats was inhibited >90% by 1 mM PTU, but was inhibited /=30 d after thyroidectomy it was 11 times the PTU-insensitive activity in controls. At the latter time, PTU-sensitive rT(3) 5'-deiodinase activity appeared to be decreased. The increase in PTU-insensitive T(4) and rT(3) 5'-deiodination observed 48 h after thyroidectomy was prevented by replacement doses of T(4) or T(3). The PTU-insensitive activity of long term hypothyroid pituitaries was decreased by 71% and >/=84% 4 h after injection of 20 and 200 mug T(3), respectively, with no change in PTU-sensitive rT(3) deiodination. These data show that rat pituitary tissue contains two distinct iodothyronine 5'-deiodinating pathways that differ with respect to substrate specificity, PTU sensitivity, reaction kinetics, and regulation by thyroid hormone. One of these resembles the 5'-deiodinase of liver and kidney, and predominates in euthyroid pituitary tissue in vitro. The other, also found in rat brain, predominates in hypothyroid pituitary tissue, is rapidly responsive to changes in thyroid hormone availability, and, as judged by previous, in vivo studies, appears to account for all the T(3) produced locally in the pituitary and, thereby, 50% of the intracellular T(3) in this tissue.
194 citations
TL;DR: These studies suggest that the epidermal maturation that follows thyroid hormone administration is mediated by local tissue levels of EGF, and admit of a possible physiological relation between thyroid hormones and EGF during postnatal cutaneous development.
Abstract: T4 and epidermal growth factor (EGF), given exogenously, both promote similar maturational events in the skin of newborn mice, i.e. precocious incisor eruption and eyelid opening. Moreover, T4 markedly increases the concentration of EGF in developing mouse submandibular glands. To examine the effect(s) of thyroid hormones on local cutaneous levels of EGF, a rapid and sensitive double antibody RIA was developed and standardized for newborn mouse skin. After fixed daily injections of T4, immunoreactive EGF concentrations in whole skin homogenates showed a dose-dependent increase when measured on postnatal days 4, 6, and 17. A similar increase was seen after T3 treatment, but administration of the structurally similar, metabolically inactive analog rT3 produced no significant effect on EGF concentrations. Induction of experimental hypothyroidism with propylthiouracil (PTU) and methimazole produced a relative decrease in skin EGF levels on postnatal day 8. Maternal sialoadenectomy did not result in a significant decrease in neonatal skin EGF, suggesting the presence of an extrasalivary source(s). These studies suggest that the epidermal maturation that follows thyroid hormone administration is mediated by local tissue levels of EGF. Moreover, the results admit of a possible physiological relation between thyroid hormones and EGF during postnatal cutaneous development.
89 citations
TL;DR: Data indicate a close inverse relationship between PTU dose and both thyroid hormone biosynthesis and peripheral T4 deiodination, and short and long term PTU treatments have quantitatively similar effects on thyroid function, although recovery of thyroid function is prolonged after long term treatment.
Abstract: Using a sensitive and specific RIA for propylthiouracil (PTU), we examined the effects of short term (1 week) and long term (1 month) PTU treatment on thyroid function in the rat, and correlated changes in thyroid function with serum and thyroid PTU levels. After 1 week, dose-dependent decreases in thyroid PBI, serum T4, and serum T3 were observed, with concomitant elevations in the serum rT3 to T4 ratio and serum TSH. Fifty percent suppression of thyroid PBI occurred at a PTU concentration in the drinking water of 0.0005% (ED50), with concomitant serum and thyroid PTU levels of 0.3 micrograms/ml and 300 ng/thyroid, respectively. After 1 month of PTU, serum T4 values were lower than after 1 week of treatment for all PTU concentrations, but values for the other thyroid functional variables were similar to those in the 1 week group at comparable PTU dosage. The PTU dose-response curve for thyroid PBI was similar to that seen after 1 week of treatment, with an ED50 of 0.0004%. After discontinuation of PTU treatment, PTU disappeared from serum in a biexponential fashion, with an early rapid distribution phase (t 1/2 = approximately 4 h) and a second slower elimination phase (t 1/2 = approximately 2.6 days). In the thyroid, an initial increase in PTU content was seen up to 18 h after PTU withdrawal; thereafter, thyroid PTU declined linearly, with a t 1/2 of 1.4 days in both groups. After PTU withdrawal, thyroid PBI recovered with a t 1/2 of 1.09 days after 1 week on PTU, but recovery was prolonged (t 1/2 = 2.8 days) after 1 month of treatment. Log thyroid PTU and log thyroid PBI were linearly related after PTU withdrawal (r = 0.97; P less than 0.001) after 1 week but not after 1 month. Serum T4 and serum T3 remained below control values for 2 days, but then rapidly normalized, with T3 values rising transiently above the control value. This rebound occurred at a time when PTU was still present within the thyroid, before thyroid PBI had returned to baseline. These data indicate a close inverse relationship between PTU dose and both thyroid hormone biosynthesis and peripheral T4 deiodination. In addition, short and long term PTU treatments have quantitatively similar effects on thyroid function, although recovery of thyroid function is prolonged after long term treatment. The biexponential disappearance of PTU from the serum is compatible with a two-compartment model of PTU distribution. The early increase in thyroid PTU after drug withdrawal is suggestive of an inhibitory effect of PTU upon its own uptake by the thyroid, whereas the faster disappearance of PTU from the thyroid than from serum is consistent with intrathyroid drug metabolism.
79 citations
TL;DR: It is suggested that TSH, in an action probably mediated by cAMP, induces synthesis of iodothyronine deiodinases in the thyroid gland.
Abstract: The effects of TSH on iodothyronine 5- and 5'-deiodinations were investigated using cultured thyroid tissues from patients with Graves' disease. The addition of TSH to the culture medium stimulated all of the iodothyronine-deiodinating activities of thyroid tissues cultured for more than 4 days. Peak TSH-induced activities were found on the fifth day of culture, and increased activities were found up to 9 days. On the fifth day of culture, TSH enhanced both outer and inner ring monodeiodinations in a dose-responsive manner between 62.5 and 250 microU/ml. This stimulation by TSH was blocked by the addition of actinomycin D or propylthiouracil. Incubation of thyroid tissues with (Bu)2cAMP mimicked the action of TSH, and theophylline potentiated the action of TSH. These results suggest that TSH, in an action probably mediated by cAMP, induces synthesis of iodothyronine deiodinases in the thyroid gland.
61 citations
TL;DR: No evidence was obtained that thyroidal accumulation of PTU or one of its metabolites could explain the prolonged inhibitory effect of this drug, and it seemed more likely that this was attributable to TPO inactivation.
Abstract: We have previously shown that the thioureylene antithyroid drugs 6-propyl-2-thiouracil (PTU) and 1-methyl-2-mercaptoimidazole (MMI) can inactivate thyroid peroxidase (TPO) in a model iodination system containing relatively high concentrations of iodide. The purpose of the present study was to determine whether these drugs may also inactivate TPO in vivo in rats. Assays for total TPO activity after injection of PTU or MMI did not prove to be a valid approach. As TPO inactivation might be expected to result in a relatively prolonged inhibition of enzyme activity, most of our experiments involved measurement of the duration of the inhibitory effect of a single injection of drug. Young rats were injected with low doses of PTU or MMI, and the effect on thyroidal organic iodine formation was determined at intervals after injection, either by 1-h pulse labeling with 131I- in vivo or by incubation of excised thyroid lobes in a medium containing 131I-. Results of both types of experiment demonstrated that the inhibitory effect of a small dose of PTU (1 mumol/100 g BW) was still very marked 17-18 h after injection. Moreover, an inhibitory effect of this small dose of PTU on the metabolism of [35S]MMI could also be demonstrated. Administration of MMI to rats, on the other hand, did not show the prolonged inhibitory effect observed with PTU. This is most likely attributable to the much lower thyroidal uptake of MMI than of PTU in rats. Intrathyroidal metabolism of [35S]PTU and [35S]MMI was also investigated. In contrast to the rapid disappearance of 35S from plasma, both drugs showed accumulation and retention of 35S in the thyroid. However, we obtained no evidence that thyroidal accumulation of PTU or one of its metabolites could explain the prolonged inhibitory effect of this drug. It seemed more likely that this was attributable to TPO inactivation. The clinical implications of our findings are discussed with relation to the dosage schedule commonly employed in the treatment of Graves' disease with antithyroid drugs.
50 citations
TL;DR: In vitro conversion of T4 to T3, T3 to 3,3′-diiodothyronine (T2), and rT3 to T2 by canine thyroid, liver, and kidney homogenate was examined, and TSH markedly stimulated thyroidal inner and outer ring iodothyronines-monodeiodinating activities.
Abstract: To investigate the effect of TSH administration on thyroidal iodothyronine-deiodinating activity, in vitro conversion of T4 to T3, T3 to 3,3′-diiodothyronine (T2), and rT3 to T2 by canine thyroid, liver, and kidney homogenate was examined, comparing tissues from TSH-treated dogs (3 IU bovine TSH daily for 3 days) with tissues from sex- and weight-matched saline-treated controls. The in vitro conversion activities were studied in the presence of 4 mM dithiothreitol at pH 6.5 for outer ring (T4 to T3 and rT3 to T2) and at pH 7.8 for inner ring (T3 to T2) deiodination. Iodothyronine-monodeiodinating activity in dog thyroid is heat labile (inactivated at 56 C × 5 min) and pH dependent, inhibited by propylthiouracil (0.2 mM) and ipodate (0.2 mM), unaffected by methimazole (up to 4 mM), ascorbate (up to 0.1 M), or KI (up to 4 mM), and is localized in the microsomal fraction. TSH markedly stimulated thyroidal inner and outer ring iodothyronine-monodeiodinating activities. Baseline rates of T4 to T3, T3 to T2, an...
42 citations
TL;DR: It appears that the effects of chemical thyroidectomy on mature and immature rat brain are different for the substance P system, suggesting that thyroxine plays an important role in the maturation of substance P-containing neurons.
41 citations
TL;DR: Receptor binding studies carried out on the striata from rats sacrificed 48 h after a 6-day course of chronic haloperidol treatment revealed a significant upregulation (increase) of dopamine receptors in the hypothyroid rats only, consistent with the hypothesis that altered thyroid status can modify the sensitivity of serotonin receptors.
Abstract: Rats made hypothyroid by the chronic oral administration of 200 mg/kg propylthiouracil were less sensitive to the cataleptic effects of haloperidol (0.1 mg/kg) treatment than were euthyroid rats chronically treated with isotonic saline. However, rats made hyperthyroid by the chronic injection of 200 micrograms/kg thyroxine were not more sensitive to the cataleptic suppressant effects of haloperidol (0.1 mg/kg). Higher doses of haloperidol (1 and 5 mg/kg) produced significantly greater catalepsy in the hyperthyroid rats and significantly reduced catalepsy in the hypothyroid rats. Receptor binding studies carried out on the striata from rats sacrificed 48 h after a 6-day course of chronic haloperidol (0.1 mg/kg once daily) treatment revealed a significant upregulation (increase) of dopamine receptors in the hypothyroid rats only. These findings are consistent with the hypothesis that altered thyroid status can modify the sensitivity of dopamine receptors.
36 citations
TL;DR: A 15‐year‐old woman with thyrotoxicosis controlled by propylthiouracil presented with chills, fever, splenomegaly, anemia, thrombocytopenia, leukopenia, hypergammaglobu‐linemia, immune complexes, a positive anti‐nuclear antibody test, and a cellular marrow with normal maturation.
TL;DR: It is concluded that measurements of AF concentrations of thyroid hormones and TSH do not reliably predict fetal or neonatal thyroid status.
Abstract: In this study we report measurements of amniotic fluid (AF) concentrations of iodothyronines and TSH in 69 normal and 16 complicated pregnancies. The latter group included 2 women with untreated hyperthyroidism, 1 patient with untreated hypothyroidism, 5 hyperthyroid patients who received propylthiouracil (3 with Graves' disease, 1 with a multinodular goiter, and 1 with chronic thyroiditis), 3 women with Graves' disease who were hypothyroid after treatment, but who were receiving replacement therapy, and 5 anencephalic pregnancies. AF hormone levels could not be correlated with either maternal or cord serum values, neonatal serum measurements, and/or the clinical status of the infant. AF TSH and T4 levels were markedly elevated in 1 patient with Graves' disease and severe Rh isoimmunization and in 2 pregnancies complicated by anencephaly without identifiable pituitary tissue in the fetus. We conclude that measurements of AF concentrations of thyroid hormones and TSH do not reliably predict fetal or neonat...
TL;DR: It is suggested that allergic mechanism may be triggered in most of Graves' patients who were administered methimazole or propylthiouracil, although there was no correlation between antithyroid autoantibodies and development of the side effects.
Abstract: In order to investigate the incidence of side effects of antithyroid drugs and to study if there were any factors related to the onset of the side effects, clinical and laboratory findings were examined in 71 untreated Graves' patients. The overall incidence was 28.2% among 71 cases who were initially administered methimazole or propylthiouracil. The incidences were 23.2% (13 of 56 cases) for methimazole and 46.7% (7 of 15 cases) for propylthiouracil, respectively, which were significantly higher than those previously reported. Seventeen of 20 cases with side effects under the drug of first choice were administered the another antithyroid drug. Four of 17 (23.5%) cases successively had side effects. The side effects were observed within 1.5 months of administration of less than 150 tablets in total in most of the cases. The serum concentration of Ig-E and peripheral eosinophils(/mm3) at the onset of the side effects were significantly higher than those before treatment. These results suggest that allergic mechanism rather than accumulating may concern the onset of side effects. Since in cases without the side effects the peripheral eosinophils at 3 to 4 weeks after administration were significantly higher than those before treatment and 19 of 51 (38.0%) cases without side effects had a high concentration of Ig-E of more than 500 u/ml, it is suggested that allergic mechanism may be triggered in most of Graves' patients who were administered methimazole or propylthiouracil. Thus, immunological disturbances in Graves' disease seems to be the cause of the side effects of antithyroid drugs, although there was no correlation between antithyroid autoantibodies and development of the side effects.
TL;DR: This family with thyroid hormone resistance had the unusual feature of clinical heterogeneity; the two children had mainly pituitary resistance to thyroid hormone and were hyperthyroid; the euthyroid father, on the other hand, had generalized tissue resistance to thyrotropin-releasing hormone.
TL;DR: Fatty liver with marked steatosis could be produced through synergic actions of PTU and DD in chicks maintained at 21 degrees C through interactions between temperature, thyroid status and synthetic oestrogen treatments.
Abstract: 1. Hepatic lipid content, lipogenic enzyme activity and plasma lipid concentration were measured in chicks reared at 21 degrees or 34 degrees C and after thyroxine (T4), thiouracil (TU), propylthiouracil (PTU), dienestrol diacetate (DD) or PTU with DD had been given for 14 d. 2. At 34 degrees C there was a significant increase in the total liver lipid and triglyceride content. 3. Injections of T4 decreased liver lipid content whereas it was increased by feeding PTU or DD. The effects of PTU were more pronounced at 21 degrees C while those of DD were more pronounced at 34 degrees C. 4. There were significant interactions between temperature, thyroid status and synthetic oestrogen treatments on total lipid and triglyceride content of the liver. Fatty liver with marked steatosis could be produced through synergic actions of PTU and DD in chicks maintained at 21 degrees C.
TL;DR: The present findings suggest that the production of T3 in liver and kidney, and its subsequent release into the blood, may provide a mechanism for the regulation of plasma T3 levels but is not a direct source of their nuclear T3.
Abstract: The effect of prolonged oral administration of PTU and MMI on the local conversion of T4 to T3 was studied in T4-maintained athyreotic rats. For this purpose the rats were equilibrated with [125I]T4 and [131I]T3 by means of continuous iv infusions. PTU treatment reduced the MCR of both T4 and T3, as well as the T3 levels in plasma, muscle, liver, kidney and cerebellum. In the cerebral cortex the total intracellular T3 concentration was not affected, while in the pituitary it even increased. The amount of T3 derived from local conversion of T4 to T3 (LcT3(T4)) was reduced in the liver. PTU treatment did not influence Lc T3(T4) in the cerebellum, but did cause an increase in the amount of T3 derived from this source in the cerebral cortex and the pituitary gland (both the homogenate and the nuclear fraction). The results indicate that in contrast to that in liver, local T3 production in the brain and pituitary must occur predominantly via a pathway which is not inhibited by PTU. In MMI-treated rats the total T3 concentration in the cerebral cortex and cerebellum was not altered, whereas both the MCR of T3 and the T3 levels in plasma and various other tissues were elevated. The relative contribution of Lc T3(T4) increased in liver and was reduced in the cerebral cortex, cerebellum and pituitary gland. In all experiments in liver the contribution of Lc T3(T4) to nuclear T3 was negligible, whereas this was not the case for the other hepatic subcellular fractions. As in liver, virtually all renal nuclear T3 was derived from plasma. The present findings suggest that the production of T3 in liver and kidney, and its subsequent release into the blood, may provide a mechanism for the regulation of plasma T3 levels but is not a direct source of their nuclear T3. In the pituitary gland and the brain local T4 to T3 conversion functions as a source of T3 for the control of local utilization. In this respect the maintainance of constant T3 levels in the brain might be important. These differences among tissues suggest that different mechanisms are involved in T4 5'-deiodination.
TL;DR: The logarithmic relationship between thyroid PTU and PTU dose suggests a saturable uptake mechanism forPTU by the thyroid, and the pharmacokinetic data are consistent with a multicompartmental model for PTU distribution.
Abstract: We have developed a highly sensitive and specific RIA for propylthiouracil (PTU) which uses 125I-labeled PTU as the radioactive ligand. At a final antibody dilution of 1:10,000, the detection limit for PTU was 100 pg; cross-reactivity with circulating, urinary, and intrathyroid PTU metabolites was negligible. Using this assay, serum and thyroid PTU levels were determined after short term (1 week) and long term (1 month) PTU treatment at doses of 0.0001-0.05%. Serum PTU was a linear function of the PTU dose (r = 0.99; P less than 0.001), whereas thyroid PTU was a linear function of the logarithm of the PTU dose (r = 0.99; P less than 0.001). Serum PTU levels were higher after 1 month of treatment than after administration for 1 week, probably because steady state conditions were not achieved after 1 week. At several doses, thyroid PTU levels were also higher after 1 month of treatment, but the differences were not as striking as those seen in the serum levels. The pharmacokinetic data are consistent with a multicompartmental model for PTU distribution. The logarithmic relationship between thyroid PTU and PTU dose suggests a saturable uptake mechanism for PTU by the thyroid; inhibition of thyroid PTU uptake by PTU itself could also explain these observations.
Journal Article•
TL;DR: Thyroids from rats chronically stimulated for 14 days showed an increase in ornithine decarboxylase following TSH administration similar to that of control rats, suggesting changes in the activation as well as specific activity of Types I and II protein kinase during hypertrophy and hyperplasia underlie the complexity of a cyclic AMP-mediated response.
Abstract: After 2 weeks of goitrogen treatment [propylthiouracil (PTU), 0.02% in drinking water], the thyroids of rats increased to 280% of control wet weight, 270% of dry weight, and 250% of control DNA content. Two phases of growth were apparent, an initial hypertrophy phase lasting 3 days (increase in cell size and gland weight with no detectable increase in DNA) and a hyperplastic phase (increase in DNA with histological evidence of cell proliferation) starting at 3-4 days and continuing through 14 days. The cyclic AMP-dependent protein kinase activity ratio (-cyclic AMP/+cyclic AMP) showed a biphasic pattern during the 2-week thyroid growth period, with maxima at day 1 (132% of control) and day 6 (148% of control). Ornithine decarboxylase (EC 4.1.1.17), the initial enzyme in polyamine biosynthesis, showed a similar biphasic pattern with a 6- to 7-fold elevation in activity at 2-3 days and a 4-fold elevation at 6 days. S-Adenosyl-L-methionine decarboxylase (EC 4.1.1.50), the enzyme which catalyzes spermidine synthesis, was elevated 4-fold at 9 days of treatment. The thyroid total supernatant protein kinase activity (+cyclic AMP) increased to 160% of control by 4 days, returning to control by 14 days of PTU treatment. The thyroid had 10% Type I activity and 90% Type II cyclic AMP-dependent protein kinase activity. The specific activity of both Types I and II remained unchanged for the first 2 days of PTU treatment. Both types increased to 150% of control by 4 days. Type I remained elevated throughout the remainder of the 14 days, in contrast to Type II, which decreased conspicuously to control levels by 6 days. A single injection of thyroid-stimulating hormone (TSH, 1.0 unit/100 g of body weight, i.p.) resulted in a 20-fold increase in thyroid ornithine decarboxylase activity by 4 hr. The same dose of TSH produced only a 3-fold induction of ODC in rats hypophysectomized 2 weeks previously. The thyroid specific activity of Types I and II protein kinase was only 55% and 57% of control, respectively, in these unresponsive rats. Thyroids from rats chronically stimulated for 14 days showed an increase in ornithine decarboxylase following TSH administration similar to that of control rats. Changes in the activation as well as specific activity of Types I and II protein kinase during hypertrophy and hyperplasia underlie the complexity of a cyclic AMP-mediated response.
TL;DR: The results suggest the hypothesis that, similarly to a decrease of serum T3, LPS activates neurones in the CNS which secrete the thyrotropin-releasing hormone (TRH), which elicits cardiorespiratory adjustments similar to those observed in the cold, while the opposite response occurs if these TRH secreting neurones are inhibited.
Abstract: Rabbits in a warm environment reacted to i.v. injections of 10 mg/kg propylthiouracil (PTU) with an immediate fall of serum triiodothyronine (T3) concentration, associated with decreases of respiratory rate and cutaneous blood flow. Simultaneously renal blood flow increased, while arterial blood pressure fell slightly. A rise in the animals' core temperature by 1.1 degree C, on average, contributed to the impression that PTU mimicked the stimulation of the normal thermoregulatory response pattern of cold defence. The cardiorespiratory responses to PTU were found to be augmented 6-8 days after thyroidectomy, but were completely abolished 16-20 days after thyroidectomy or chronic PTU treatment. In chronically thyroidectomized rabbits, i.v. injections of T3, but not of T4, elicited panting and cutaneous vasodilatation. The acute effects of injecting i.v. bacterial endotoxin (LPS) into rabbits in a warm environment consisted of cutaneous vasoconstriction and a decrease in respiratory rate, i.e. in an autonomic cold defence response, which was associated with a sustained increase in serum T3 concentration and caused core temperature, T3 serum concentration decreased again, whilst simultaneously the autonomic activity pattern changed to that of heat defence, comprising a rise in respiratory rate and skin vasodilatation. The results suggest the hypothesis that, similarly to a decrease of serum T3, LPS activates neurones in the CNS which secrete the thyrotropin-releasing hormone (TRH). This, in turn, elicits cardiorespiratory adjustments similar to those observed in the cold, while the opposite response occurs if these TRH secreting neurones are inhibited.
TL;DR: It is suggested that monitoring the serum PTU levels in patients with Graves' disease can be of clinical value in patients who do not respond to treatment, and may provide some clues as to the mechanism by which toxic reaction develops.
Abstract: The serum levels of propylthiouracil (PTU) were determined by radioimmunoassay in 10 normal subjects and in 11 patients with Graves' disease after a single 100 or 200 mg oral dose of PTU. The serum half-life of PTU in the normal subjects and in hyperthyroid patients with uneventful clinical course was 75 +/- 19 min (mean +/- SD, n = 6) and 73 +/- 13 min (n = 7), respectively. Maximum serum PTU concentrations were usually attained within 1 h after a single 200 mg oral dose and at 1 h were 5.3 +/- 1.4 micrograms/ml (3.1 +/- 0.82 X 10(-5) M) in normal subjects (n = 6) and 4.8 +/- 2.4 micrograms/ml (2.8 +/- 1.4 X 10(-5) M) in hyperthyroid patients (n = 7). These between-group differences were not significant. Serum PTU concentrations were low in a pregnant hyperthyroid patient with a weak response to PTU treatment. In another patient, who appeared resistant to PTU therapy, the serum PTU level increased as expected at testing, and it was later confirmed that, during treatment, he had not taken the drug as prescribed. In a patient who developed agranulocytosis due to methimazole and subsequently fever due to PTU, the half-life of PTU was prolonged to about 130 min. These findings suggest that monitoring the serum PTU levels in patients with Graves' disease can be of clinical value in patients who do not respond to treatment. Furthermore, it may provide some clues as to the mechanism by which toxic reaction develops.
TL;DR: A 47-yr-old woman who had previously received methimazole (MMI) treatment for hyperthyroidism was found to have glucagon binding autoantibodies in plasma, suggesting that the development of glucagon antibodies in hyper thyroidroidism may be associated with MMI treatment.
Abstract: A 47-yr-old woman who had previously received methimazole (MMI) treatment for hyperthyroidism was found to have glucagon binding autoantibodies in plasma. She had never received glucagon. The binding substances were detected in plasma at the time of a glucagon RIA. [125I] Glucagon binding was inhibited only by porcine glucagon and porcine glicentin, and dissociated at acid pH. The substances proved to be glucagon binding antibodies (immunoglobulin G, L-chain K-type), as determined by ammonium sulfate and radioprecipitation. There were no clinical manifestations related the presence of these autoantibodies. In a survey of 91 patients with thyroid disease, 3 patients whose plasma bound [125I]glucagon were identified among 41 with hyperthyroidism who were receiving MMI treatment. Such binding was not found in plasma from untreated hyperthyroid patients, those receiving propylthiouracil or those with chronic thyroiditis. These findings suggest that the development of glucagon antibodies in hyperthyroidism may...
Journal Article•
TL;DR: Lympho-stimulation by MMI was evident regardless of the time of MMI addition, thus indicating that MMI is, by its action, a lymphoid stimulator and may lead to the insulin autoimmune syndrome in predisposed subjects with underlying Graves' disease.
Abstract: Using peripheral blood lymphocytes from 8 healthy individuals and 5 patients with untreated Graves' disease, direct effects of methimazole (MMI) and propylthiouracil (PTU) on lectin-induced lymphocyte proliferative response were studied. Lymphocytes were cultured for 72 hr in the presence of lectins and antithyroid drugs. Lymphocyte DNA synthesis was counted by incorporation of 3H-thymidine. MMI at 1,000 microM enhanced lectin-induced lymphoproliferation of peripheral blood lymphocytes from both patients with Graves' disease and healthy individuals, at every point of culture time, while PTU showed a tendency toward suppression. These results suggest that this lympho-stimulation by MMI may be a causative factor related to insulin autoimmune syndrome, as deduced from the clinical reports that insulin autoimmune syndrome is, sometimes, found in patients with Graves' disease treated with MMI. This lympho-stimulation was evident regardless of the time of MMI addition, thus indicating that MMI is, by its action, a lymphoid stimulator and may lead to the insulin autoimmune syndrome in predisposed subjects with underlying Graves' disease.
TL;DR: This is, to the best of the authors' knowledge, the first report of a case in which agranulocytosis followed treatment with both propylthiouracil and methimazole in the same patient.
Abstract: A 45-year-old woman with thyrotoxicosis developed agranulocytosis after treatment with propylthiouracil. When the thyrotoxicosis recurred, accompanied by a severe psychotic reaction, administration of antithyroid medication was recommenced. The patient was given methimazole instead of propylthiouracil but, 10 weeks later, agranulocytosis again occurred. This is, to the best of our knowledge, the first report of a case in which agranulocytosis followed treatment with both propylthiouracil and methimazole in the same patient.
TL;DR: Data suggest that antithyroid drug accumulation by this tissue is not dependent on the anion trap; the localization of drug and iodide at the site of peroxidase activity suggest that this may be an important factor in the mechanism of drug accumulation.
Abstract: [35S]Methimazole and [35S]propylthiouracil were shown to accumulate in mouse submandibular gland in vivo, with maximal tissue: plasma ratios being achieved at the lowest dose of drug studied (0.1 microgram/animal). Autoradiography of submandibular glands showed that the drugs were localized to the intralobular ductal epithelium and within the lumen of the convoluted granular tubule, which was identical to the localization of radiolabelled iodide. Histochemical studies indicated that this was the site of peroxidase activity within the gland. Drug accumulation persisted when iodide trapping was competitively inhibited using perchlorate. These data suggest that antithyroid drug accumulation by this tissue is not dependent on the anion trap; the localization of drug and iodide at the site of peroxidase activity suggest that this may be an important factor in the mechanism of drug accumulation, possibly related to subsequent drug metabolism.
TL;DR: Serum protein binding of propylthiouracil was measured by ultrafiltration in healthy and hyperthyroid patients and interaction with acetylsalicylic acid, warfarin and phenylbutazone, but not with antipyrine and nortriptyline or other basic drugs.
Abstract: Serum protein binding of propylthiouracil (PTU) was measured by ultrafiltration in healthy and hyperthyroid patients. The serum protein binding in 12 euthyroid subjects was 76.2 +/- 1.2% (mean +/- s.d.), not significantly different from the values in 10 hyperthyroid patients: 76.6 +/- 1.3% Binding was unaffected by incubation time and temperatures between 25 and 37 degrees C, but increased from 76.5 to 79.1% when pH changed from 7.4 to 7.9. PTU is predominantly bound to albumin with two classes of binding groups with different number of binding sites and affinity. Displacement experiments showed interaction with acetylsalicylic acid, warfarin and phenylbutazone, but not with antipyrine and nortriptyline or other basic drugs.
01 Jan 1983
TL;DR: Results indicate that propylthiouracil administration in the fasting state is more advisable for obtaining a consistent bioavailability.
Abstract: Pharmacokinetics of propylthiouracil after a single oral dose were studied in six pediatric patients with Graves disease, with respect to influence of food intake. Propylthiouracil administration in the fasting state induced a rapid rise of plasma level reaching a peak of 30 to 60 min. Peak values ranged from 7.2 to 18 micrograms/ml with administered dose (100 to 280 mg/m2 BSA) and plasma half-life was 1.3 +/- 0.41 hr (mean +/- SD). Single compartment model with first order absorption showed excellent fit to the data obtained in the fasting state, but not in the fed state. Most individuals showed marked difference in the pattern of propylthiouracil concentration-time curves between the fasting and the fed state. Food intake prior to the drug ingestion was associated with lower and delayed peak and variable AUC values. These results indicate that propylthiouracil administration in the fasting state is more advisable for obtaining a consistent bioavailability.
TL;DR: PA and SPA in the thyroid from 29 patients with Graves' disease treated with propylthiouracil or methimazole did not correlate with serum thyroid hormone level immediately before surgery, but there were good correlations among PA, SPA and PA per DNA content of the thyroid tissue.
Abstract: Although the activity of lysosomal protease in Graves' thyroid is considered to be increased, there has been no quantitative method to estimate the protease activity in the thyroid tissue due to the contamination of thyroglobulin (Tg) which varies in susceptibility to the protease. In the present study, the proteolytic activity (PA) of thyroid lysosomal protease preparation (P25) separated from Tg was assayed using 125 I labeled rat Tg. More than 95% of 125 I-Tg was hydrolyzed at pH 4.0 without deiodination, and the pattern of liberated iodoamino acids resembled that of pronase digest except for a higher T 3 T 4 ratio Thirty-seven Graves' thyroids and 15 paranodular thyroid tissues were assayed. PA, the specific PA (SPA; calculated as PA per mg P25 protein) and PA per DNA content in Graves' thyroids were significantly higher than those in controls. There were good correlations among PA, SPA and PA per DNA content of the thyroid tissue. PA and SPA in the thyroid from 29 patients with Graves' disease treated with propylthiouracil or methimazole did not correlate with serum thyroid hormone level immediately before surgery. In 8 patients treated with KI, PA from 5 patients whose serum thyroid hormone levels had been normalized were significantly lower than those from 3 patients who were still thyrotoxic. This suggests that one of the mechanism involved in the suppressive effect of excess iodide on the secretory process of the Graves' thyroid may be the inhibition of lysosomal protease.
TL;DR: The present findings appear to be consistent with the view that TSH is not the unique factor determining the size of the resulting goitre, and the different endocrine and metabolic states of rats on PTU or PTU + ClO4, shown by their different plasma insulin, GH and glucose levels, may play an important role in determining the thyroid weight response to TSH.
Abstract: In this study we investigated further the antigoitrogenic effect of ClO4 in rats on a low iodine diet (LID) and 6-propyl-2-thiouracil (PTU). The thyroid weight of rats on the mixed goitrogen was initially similar to that of animals on PTU, decreasing to values obtained in rats treated with ClO4 alone by 10 days. Despite the differences in thyroid weight, rats treated during an identical period with PTU or mixed goitrogen develop hypothyroidism to a comparable degree as far as can be assessed by the thyroidal 127I content, plasma T4, T3 and TSH concentrations, and pituitary TSH content. Moreover, it was observed that there were differences in plasma insulin and glucose levels in these hypothyroid animals. The plasma insulin and glucose levels of rats on PTU are comparable to those found in control rats. In rats on mixed goitrogen, both plasma insulin and glucose levels are initially maintained within the normal ranges, and then decline over the subsequent days of treatment. Within the treatment period studied here, plasma insulin and glucose levels were higher for rats on PTU than for animals on ClO4, PTU + ClO4, or thyroidectomized (Th) animals. We have obtained further evidence of the hypothyroid state of rats on these goitrogen regimens based on measurements of pituitary and plasma GH levels and liver mitochondrial alpha-glycerophosphate dehydrogenase (alpha-GPD). The PTU-treatment decreased the liver alpha-GPD activity to a comparable degree to that of mixed goitrogen. Moreover, both PTU + ClO4 and PTU-treatment resulted in a state of hypothyroidism intense enough to induce effects on growth, and plasma and pituitary GH levels comparable to that of Th animals. However, the values for rats on mixed goitrogen appear to be below the PTU data. The present findings appear to be consistent with the view that TSH is not the unique factor determining the size of the resulting goitre. The results are discussed in relation to the hypothesis that: 1) the antigoitrogenic effect of ClO4 could be associated with changes in the ability of the thyroid tissue to bind TSH, or with a step beyond TSH binding, and 2) the different endocrine and metabolic states of rats on PTU or PTU + ClO4, shown by their different plasma insulin, GH and glucose levels, may play an important role in determining the thyroid weight response to TSH.
TL;DR: Propylthiouracil inhibited glutathione (GSH) S-transferase (EC 2.5.1.18) activity of rat spleens in a concentration dependent manner in vitro and GSH S- transferase activity was not affected by the same treatment.
Abstract: Propylthiouracil (PTU) inhibited glutathione (GSH) S-transferase (EC 2.5.1.18) activity of rat spleens in a concentration dependent manner in vitro. PTU (1.5 mmoles/kg) treatment of rats for 1 or 2 weeks caused a decrease in leukocyte number and spleen weight. Nevertheless, GSH S-transferase activity was not affected by the same treatment.