Showing papers on "Prolactin published in 1973"
TL;DR: A sensitive homologous radioimmunoassay for human prolactin (hPRL) is developed and measures concentrations of hPRL as low as 1 ng/ml of human plasma in a group of randomly selected male and female individuals.
Abstract: We have developed a sensitive homologous radioimmunoassay for human prolactin (hPRL). Prolactin isolated from human pituitary glands was used for generating antibodies in rabbits, for iodination, and for standards. The assay is highly specific for hPRL and measures concentrations of hPRL as low as 1 ng/ml of human plasma. In this assay, the plasma concentrations of hPRL in a group of randomly selected male and female individuals averaged 13 ± 4 (SD) and 14 ± 4 ng/ml, respectively. In contrast, hPRL in the pooled plasma of pregnant women assayed 80 ng/ml; a post-partum plasma measured 215 ng/ml. Of 6 patients with acromegaly, 5 possessed hPRL levels above 34 ng/ml, the average being 40 ± 9 ng/ml. Administration of TSH releasing hormone increased plasma hPRL concentrations by 4-fold in both a male and a female subject, while LH releasing hormone depressed them slightly. The concentration of hPRL in pituitary glands removed at autopsy was 1.5 μg/mg for a male and 1.3 μg/mg for a female. These values approxim...
669 citations
TL;DR: A radioreceptor assay with a sensitivity of 5 nanograms per milliliter has been developed for mammalian and avian pituitary prolactin, placental lactogenic hormones, and humnan growth hormone, using a membrane receptor preparation isolated from rabbit mammary glands.
Abstract: A radioreceptor assay with a sensitivity of 5 nanograms per milliliter has been developed for mammalian and avian pituitary prolactin, placental lactogenic hormones, and humnan growth hormone, using a membrane receptor preparation isolated from rabbit mammary glands. Prolactin preparations inhibited the binding of [(125)I]prolactin to receptors in direct proportion to the biological potency of these preparations. Thus, the radioreceptor assay provides a convenient and simnple assay for hormones which have lactogenic activity.
433 citations
TL;DR: Serum LH concentration during the first 11 days of pregnancy was distinctly higher than during the period between days 13–19, with a conspicuous pivot—point occurring at about day 12; beginning on day 20 and continuing to term, a progressive increase occurred, which was not contiguous with the acute, post—partum, ovulation inducing surge of LH.
Abstract: Serum levels of luteinizing hormone (LH) and prolactin were measured twice daily, and those of progesterone once daily, throughout gestation in rats with confirmed pregnancies, and in which parturition was seen to have occurred on day 23. Serum LH concentration during the first 11 days of pregnancy was distinctly higher than during the period between days 13–19, with a conspicuous pivot—point occurring at about day 12; beginning on day 20 and continuing to term, a progressive increase occurred, which was not contiguous with the acute, post—partum, ovulation inducing surge of LH. Serum prolactin level did not show as distinct a pattern of change, although highly erratic levels during the initial 10 days, and consistently low levels during most of the second half of pregnancy were noted. When related to the pattern of changes in the levels of serum LH and prolactin, the changes in serum progesterone level were seen to be inversely related to those in serum LH during the period from day 11 to term (r = -0.97...
327 citations
TL;DR: The synthetic growth-hormone-release inhibitory hormone inhibits G.R.R.-I.H. response to insulin-induced hypoglycaemia without affecting the prolactin or corticosteroid responses, but the effects are short-lived.
269 citations
TL;DR: It is concluded that the nocturnal rise is dependent on the occurrence of sleep, not on the inherent rhythm related to time of day.
Abstract: Four normal young adults underwent partial or complete inversion of their sleepwaking cycles to determine the relationship of the nocturnal release of human prolactin to sleep. Prolactin release shifted immediately and completely with shifts of sleep onset of 3, 6 and 12 hr. Thus, the nocturnal rise is dependent on the occurrence of sleep and is not based on an inherent rhythm related to time of day.
249 citations
TL;DR: A sensitive radioreceptor assay (RRA) capable of detecting 0.2 ng of human growth hormone (hGH) has been developed using plasma membrane fragments derived from the liver of pregnant rabbits and 125I-hGH.
Abstract: A sensitive radioreceptor assay (RRA) capable of detecting 0.2 ng of human growth hormone (hGH) has been developed using plasma membrane fragments derived from the liver of pregnant rabbits and 125I-hGH. Human, monkey, bovine and ovine GH all inhibit the binding of 125I-hGH, while the inhibition by hPL or human prolactin (hPRL) was minimal.
245 citations
TL;DR: The results demonstrate that function and morphologic integrity are preserved in this cell system, suitable for the study of various aspects of pituitary secretion and its control.
Abstract: A new procedure has been developed for dissociating anterior pituitary tissue and producing a viable suspension of single cells. The procedure involves incubation of small tissue blocks in 1 mg/ml trypsin (15 min), followed by incubation in 8 µg/ml neuraminidase and 1 mM EDTA (15 min), followed by mechanical dispersion. Cell yields are ∼55%, based on recovered DNA. By electron microscopy five types of secretory cells (somatotrophs, mammotrophs, thyrotrophs, gonadotrophs, and corticotrophs) plus endothelial and follicular cells can be identified and are morphologically well preserved up to 20 h after dissociation. Throughout this period, the cells incorporate linearly [3H]leucine into protein for up to 4 h at a rate 90% greater than hemipituitaries, and they synthesize, transport intracellularly, and release the two major pituitary secretory products, growth hormone and prolactin. Immediately after dissociation the cells' ability to respond to secretogogues (high K+ and dibutyryl cyclic AMP) is impaired, but after a 6–12-h culture period, the cells apparently recover and discharge 24% and 52%, respectively, of their content of prelabeled growth hormone over a 3-h period in response to these two secretogogues. This represents a stimulation of 109% and 470% over that released by cells incubated in control medium. The results demonstrate that function and morphologic integrity are preserved in this cell system. Therefore it is suitable for the study of various aspects of pituitary secretion and its control.
236 citations
TL;DR: In that the pineal gland influences brain constituents and, possibly, synaptic transmission, it is likely that it may control the peripheral organs of internal secretion by a mechanism involving corticol indoleamine and catecholamine concentrations.
Abstract: Literature on the endocrinologic function of the pineal gland is reviewed. The pineal gland appears to have an inhibitory effect on gonadtoropin release. It is possible since no hypothalamic inhibiting factors have been indentified with the control of luteinizing hormone (LH) and follicle stimulating hormone synthesis and release by the anterior pituitary that the pineal gland provides the necessary inhibitory principles. The antigonadotropic activity of pineal polypeptides may be of importance in this regard. In that these polypeptides are not present in the urine of pinealectomized rats it is assumed that they are secreted by the pineal gland. Although the effects of the pineal gland on sexual physiology in animal experiments performed under phototropic conditions are barely detectable it is incorrect to assume that the organ has no function. Exposure to artificial light for 12-16 hours may severely bias or negate the effect of the pineal gland. In that the pineal gland influences brain constituents and possibly synaptic transmission it is likely that it may control the peripheral organs of internal secretion by a mechanism involving corticol indoleamine and catecholamine concentrations.
201 citations
TL;DR: Synthetic (linear) somatostatin (SRIF, somatotropin-release inhibiting factor) abolished the elevation of serum GH concentration induced in normal human subjects by the administration of L-dopa and arginine.
Abstract: Synthetic (linear) somatostatin (SRIF, somatotropin-release inhibiting factor) abolished the elevation of serum GH concentration induced in normal human subjects by the administration of L-dopa and arginine. Within the dose used (250 μg, iv and 500 μg constant infusion) somatostatin. did not inhibit the rise in circulating PRL normally observed with arginine infusion nor did it modify basal levels of serum GH, TSH, PRL, FSH and LH.
196 citations
TL;DR: Within—stage of— lactation correlations between serum prolactin and milk yield were very low and sometimes negative during early lactation, but after 12 to 24 weeks of lactation the correla...
Abstract: Serum prolactin was measured in 55 cows 2–4 hr before, immediately after and 1 hr after milking for the duration of lactation or week 44, whichever occurred first. Serum prolactin increased in response to stimuli associated with milking, but this response was largest at 8 weeks; of lactation (77 ng/ml) and then gradually decreased as lactation advanced until at 32 weeks prolactin was no longer released. As prolactin concentrations increased in the pre—milking serum samples the amount subsequently released by the milking stimulus was reduced (p < 0.01). The correlation between serum prolactin measured 2 to 4 hr before milking and milk yield was very low (r = -0.03), although similar calculations for samples collected immediately after and 1 hour after milking (r = 0.36 and 0.18, respectively) were significant (p < 0.01). Within—stageof— lactation correlations between serum prolactin and milk yield were very low and sometimes negative during early lactation, but after 12 to 24 weeks of lactation the correla...
194 citations
TL;DR: The action of TRH on GH3 cells involves an initial binding of the tripeptide to specific receptors, which has a pH optimum of 7.5, does not require the presence of divalent cations, and is inhibited by high concentrations of calcium ion.
TL;DR: The results support the concept that the effect of L-tryptophan on the secretion of human prolactin is mediated through its conversion to serotonin and are consistent with reported experimental observations that serotonin may participate in the reciprocal regulation of Prolactin and gonadotropins.
Abstract: Previous studies have demonstrated that the secretion of human prolactin is regulated primarily by factors that influence catecholamines of the hypothalamus. In an effort to identify other factors that may regulate prolactin secretion, the amino acid L-tryptophan, a precursor in the synthesis of serotonin, was infused into normal human volunteers. Intravenous infusion of L-tryptophan, 5-10 g over a 20 min period, but not equivalent amounts of 17 other amino acids, induced marked increases in serum prolactin concentrations in eight normal human volunteers. Increases of 20-200 ng/ml above the control level were observed with peak values at 20-45 min after initiation of the infusion. In addition, infusion of L-tryptophan was associated with decreases in serum concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and thyrotropin in those subjects in whom the base-line serum hormone concentration was above the lower limits of assay detectability. No consistent change was observed in serum concentrations of growth hormone, cortisol, or glucose. Four subjects with juvenile diabetes demonstrated increases in serum prolactin values comparable with those observed in healthy individuals in response to infusions of L-tryptophan. Serum prolactin values in patients with surgically induced hypopituitarism were undetectable or deficient after infusion of 10 g of L-tryptophan. In this respect, infusion of L-tryptophan was equally effective in these subjects as the standard chlorpromazine stimulation test in identifying patients with hypopituitarism, indicating that the infusion of L-tryptophan may serve as a sensitive and reliable clinical test of prolactin secretory reserve. Further studies relating to the possible mechanism of action of L-tryptophan indicated that infusion of 5-hydroxytryptophan represents a much more potent stimulus for the secretion of prolactin and that premedication with the serotonin antagonist, methysergide maleate, serves to blunt the effect of L-tryptophan on prolactin secretion. These results support the concept that the effect of L-tryptophan on the secretion of human prolactin is mediated through its conversion to serotonin and are consistent with reported experimental observations that serotonin may participate in the reciprocal regulation of prolactin and gonadotropins.
TL;DR: Plasma prolactin levels were measured by radioimmuno-assay in free-moving lactating rats bearing heart cannulas and returned to the mothers after a separation of 8–12 h fr.
Abstract: Plasma prolactin levels were measured by radioimmuno-assay in free-moving lactating rats bearing heart cannulas. Litters adjusted to 6 pups were returned to the mothers after a separation of 8–12 h fr
TL;DR: Apomorphine hydrochloride increased the concentration of growth hormone (GH) in serum above 10 ng/ml in all 12 subjects and decreased serum prolactin (PRL) levels in 4 subjects, compatible with modulation of GH secretion by a dopaminergic mechanism.
Abstract: Apomorphine hydrochloride was administered sc to 12 adult men on 23 occasions. In doses of 0.75–1.0 mg, apomorphine-HCl increased the concentration of growth hormone (GH) in serum above 10 ng/ml in all 12 subjects; peak values occurred at 30–60 min following injection. The increase was antagonized in the 4 subjects pretreated with chlorpromazine. Apomorphine decreased serum prolactin (PRL) levels in 4 subjects but only in a dose of 1.0 or 1.5 mg; the compound failed to decrease chlorpromazineinduced elevated levels of PRL. The drug had no effect on serum LH or FSH. These results are compatible with modulation of GH secretion by a dopaminergic mechanism. Further studies are needed to determine the reliability and potential clinical usefulness of apomorphine as an agent to stimulate GH secretion.
TL;DR: It is suggested that brain serotonin, its precursors and melatonin may have a role in stimulating prolactin release, and thereby serve to counter the inhibitory effects of hypothalamic catecholamines on prolactIn release.
Abstract: A single intravenous injection of tryptophane, 5-hydroxytryptophane, serotonin or melatonin was given to rats on the morning of proestrus and to hypophysectomized, pituitarygrafted female rats. The 5-hydroxytryptophane increased serum prolactin about 9 fold by 30 min after injection and about 6 fold by 1 hr after injection as compared to control values; it also doubled serum prolactin values in hypophysectomized rats with an anterior pituitary graft. Tryptophane approximately doubled serum prolactin over control values by 30 min and 2 hr after injection, but these differences were not significant statistically. Serotonin itself did not significantly alter serum prolactin levels, but melatonin significantly increased serum prolactin over control levels by 1 and 2 hr after injection. These results suggest that brain serotonin, its precursors and melatonin may have a role in stimulating prolactin release, and thereby serve to counter the inhibitory effects of hypothalamic catecholamines on prolactin release....
TL;DR: Injection of bovine growth hormone every third day improved milk production as much as the same total dose given daily, when the hormone was injected over 10 wk, milk production was stimulated for the entire period and there was no measurable development of antibodies to it.
TL;DR: There are two intracellular pools of leucine in GH cells, one of which does not appear to equilibrate readily with the medium, and the long term effects on these cells of thyrotropinreleasing hormone and hydrocortisone result only in a change in the synthesis of prolactin and not in its rate of degradation.
TL;DR: The results indicate that Eb or Tp inhibited release of LH in castrate rats of both sexes, and males were more sensitive to the inhibitor effect of the low dose of Tp than females.
Abstract: The effects of single sc injections of various doses of estradiol benzoate (Eb) and testosterone propionate (Tp) on plasma levels of LH, FSH and prolactin have been reinvestigated in castrate rats of both sexes. Our results indicate that Eb or Tp inhibited release of LH in castrate rats of both sexes. Males were more sensitive to the inhibitor effect of the low dose of Tp than females. The steroids also lowered plasma FSH levels in spayed females; however, in castrated males Eb stimulated FSH release and a decrease in FSH followed the injection of only the highest dose (2 mg) of Tp. Eb and Tp had a synergistic effect in inhibiting FSH release in the male. Both steroids stimulated release of prolactin in castrate males and females (no sex difference in release of prolactin in response to Eb was observed; however, males appeared more sensitive to Tp treatment). Single injections of progesterone (P) in spayed females produced variable results. High doses inhibited LH release and elevated prolactin levels. Ef...
TL;DR: Results show that changes from normal serum levels of T3 and T4 are associated with changes in prolactin responses to TRH; subnormal serum Levels of T2 and T3 increase TRH-induced prolact in patients before and after correction of their serum thyroid hormone abnormalities.
Abstract: The influence of serum triiodothyronine (T3) and thyroxine (T4) concentrations on the release of prolactin in man was studied by determining the prolactin response to synthetic thyrotropin-releasing hormone (TRH) in hypothyroid and hyperthyroid patients before and after correction of their serum thyroid hormone abnormalities. The maximum increment in serum prolactin above the basal level (maximum Δ prolactin) was used as the index of response to TRH.
In 12 patients with primary hypothyroidism, the maximum Δ prolactin in response to TRH fell from 100.5±29.1 ng/ml (mean ±SEM) before treatment to 36.1±6.0 ng/ml (P < 0.01) during the 4th wk of treatment with 30 μg T3 + 120 μg T4 daily. The mean serum T3 level increased from 57±8 to 138±10 ng/100 ml, and the mean serum T4 level increased from 3.0±0.4 to 7.2±0.4 μg/100 ml during this treatment. In eight normal subjects the maximum Δprolactin in response to TRH was not significantly different during the 4th wk of treatment with 30 μg T3 + 120 μg T4 daily from the response before treatment. In 10 patients with hyperthyroidism, the maximum Δprolactin in response to TRH increased from 14.2±2.9 ng/ml before treatment to 46.9±6.7 ng/ml (P < 0.001) during antithyroid treatment. The mean serum T3 level fell from 313±47 to 90±8 ng/100 ml, and the mean serum T4 level fell from 20.8±2.5 to 6.8±0.6 μg/100 ml during this treatment.
These results show that changes from normal serum levels of T3 and T4 are associated with changes in prolactin responses to TRH; subnormal serum levels of T3 and T4 increase TRH-induced prolactin release, whereas substantially higher than normal serum levels of T3 and T4 inhibit this release.
TL;DR: Treatment of 6 normal male volunteers with diethylstilbestrol 2.5 mg twice daily orally for 5 days resulted in no change in basal thyrotropin (TSH) or prolactin serum levels; TSH response to thyrotopin-releasing hormone (TRH) was not changed by estrogen pretreatment but prolactIn responses were significantly increased.
Abstract: Treatment of 6 normal male volunteers with diethylstilbestrol (DES) 2.5 mg twice daily orally for 5 days resulted in no change in basal thyrotropin (TSH) or prolactin serum levels; TSH response to thyrotropin-releasing hormone (TRH) was not changed by estrogen pretreatment but prolactin responses were significantly increased. Basal growth hormone (GH) levels were elevated by DES pretreatment, but no significant GH response to TRH was seen before or after estrogen administration.
TL;DR: Initiation of the rapid phase of testicular growth at 25 days could be correlated with the elevations of serum FSH and prolactin levels, and rapid growth of sex accessories began somewhat later in the presence of continued relatively high prol actin levels and falling levels of FSH.
Abstract: Serum levels of FSH, LH and prolactin were determined during development in male rats. Blood was collected from the trunk after decapitation. Prolactin levels were very low at 15 and 20 days of age, underwent an initial rise at 25 days, and then remained relatively constant until 50 days. A secondary increase occurred thereafter to reach maximal adult values at 90 days. Serum FSH was readily detectable at 15 and 20 days, rose to a peak at 25 and 30 days and then declined back to the original levels by 60 days. It remained relatively constant thereafter. On the other hand, serum LH levels underwent a very gradual increase from 15 days to reach a maximum at 70 days which was similar to levels found in adults. Initiation of the rapid phase of testicular growth at 25 days could be correlated with the elevations of serum FSH and prolactin levels. Rapid growth of sex accessories began somewhat later in the presence of continued relatively high prolactin levels and falling levels of FSH. Later growth of the sex ...
TL;DR: Autoradiographic analysis of serial frozen tissue sections revealed that radioiodinated protein hormones, applied topically, were bound specifically and selectively to target tissues, indicating the existence of specific intraovarian tissue-hormone binding, presumably to receptors, and suggesting that this receptor activity varies with the functional state of the intraovarians.
Abstract: Autoradiographic analysis of serial frozen tissue sections revealed that radioiodinated protein hormones, applied topically, were bound specifically and selectively to target tissues. To study relationships between the functional state of target tissues and protein hormone binding, autoradiographic analysis was performed on ovaries from rats with different known physiologic states. Changes in ovarian and pituitary function were assessed by radioimmunoassay of progesterone, luteinizing hormone (LH), follicle stimulating hormone (FSH), and prolactin in serum. Corpora lutea and interstitial tissue bound labeled rat growth hormone, ovine prolactin, and human chorionic gonadotropin (hCG). The extent of this binding varied with endogenous hormone concentrations and with the functional state of the ovary. At all times, thecal cells bound labeled hCG and granulosa cells of some moderate to large follicles bound labeled FSH. Granulosa cells bound other hormones variably. These results indicate the existence of specific intraovarian tissue-hormone binding, presumably to receptors, and suggest that this receptor activity varies with the functional state of the intraovarian tissues.
TL;DR: The effect of pGlu-His-Pro-NH2 (TRF) on the secretion of prolactin (PRL) from rat anterior pituitary glands and cell cultures derived from normal and propylthiouracil (PTU)-fed rats is reported.
Abstract: The effect of pGlu-His-Pro-NH2 (TRF) on the secretion of prolactin (PRL) from rat anterior pituitary glands and cell cultures derived from normal and propylthiouracil (PTU)-fed rats is reported. TRF only slightly increased (less than 50% over control levels) the rate of secretion of radioimmunoassayable PRL or immune precipitated biosynthesized [3H]-PRL secreted by normal anterior pituitary cells, but had a greater effect on the rate of secretion of PRL by pituitary cell cultures obtained from PTU-treated rats. Furthermore, PTU-treated rats’ hemi-pituitary glands incubated in vitro also respond to TRF, demonstrating that the response to TRF by rat tissue is not a result of the cell dispersion or culture procedure. The administration of thyroid hormones which inhibit the TRF mediated secretion of TSH in vivo and in vitro suppress the secretion of PRL by hemi-pituitaries and dispersed cell cultures of anterior pituitaries from PTU-fed rats. Comparative studies of the [3H]-TRF binding to (mouse) TSH secretin...
TL;DR: Induction of hypothyroidism by treatment of rats with propylthiouracil (PTU) or radioactive iodine reduced pituitary and plasma growth hormone concentrations and administration of cortisol to chronically Hypothyroid animals failed to increase pituitsary growth hormone content.
Abstract: Induction of hypothyroidism by treatment of rats with propylthiouracil (PTU) or radioactive iodine reduced pituitary and plasma growth hormone concentrations. Radioimmunoassayable pituitary and plasma growth hormone was diminished after three weeks of PTU ingestion. By four weeks, plasma growth hormone had fallen to barely detectable levels in most animals. Pituitary growth hormone concentration reached the lowest value by 40 days and remained depressed throughout 98 days of PTU ingestion. After treatment for 21 days with PTU, rats given tap water had progressively increasing pituitary growth hormone concentrations reaching control levels within 19 days. Rats given PTU and thyroxine injections to prevent hypothyroidism had no appreciable change in pituitary or plasma growth hormone concentrations. Administration of cortisol to chronically hypothyroid animals failed to increase pituitary growth hormone content. When rats bearing the growth hormone— and prolactin— producing tumor MtTWl5 were rendered hypoth...
TL;DR: Preliminary experiments utilizing lactating cows and dairy bulls demonstrated release of prolactin by a single iv injection of 100 Mg synthetic thyrotropin—releasing hormone (TRH) and more completely the endocrine changes occurring in the bovine after TRH.
Abstract: Preliminary experiments utilizing lactating cows and dairy bulls demonstrated release of prolactin by a single iv injection of 100 Mg synthetic thyrotropin—releasing hormone (TRH). Thereafter, a second experiment described more completely the endocrine changes occurring in the bovine after TRH. Twenty—five, 50 or 100 μg synthetic TRH was administered via jugular cannulae to each of four lactating cows. Serum prolactin immediately before TRH averaged 3.4 ng/ml. Prolactin averaged 21.1, 9.2 and 23.9 ng/ml at 2 min after 25, 50 or 100 μg TRH, respectively. Comparable values at the prolactin peak were 68.0, 23.4 and 60.6 and intervals to the prolactin peak were 10, 8 and 8 min, respectively. Serum prolactin increased in each cow after each dose of TRH, and returned to baseline within 2 hr. Serum thyroxine (μg/100 ml) increased linearly (p < 0.01) for 5 hr, but the increase was not linearly related to dose of TRH. In contrast, growth hormone increased proportionally to the dose of TRH. Total serum glucocortico...
TL;DR: The studies indicate that responses to these agents in the prepubertal child are qualitatively similar to those in adults, and significantly increased levels of prolactin are observed at a time when maximum increases in neonatal breast hypertrophy are observed clinically.
Abstract: Extract: Serum prolactin (HPr) and serum growth hormone (HGH) were determined by double antibody radioimmunoassay methods. Markedly elevated levels of serum prolactin with considerable variation were observed in the neonatal period. No significant difference was observed in six matched arteriovenous cord blood samples. No sex difference was noted in the full term infants, whereas the mean value for 24 premature male infants in the 1st week of life (190 ± 17 ng/ml sem) was significantly higher (P < 0.001) than mean values for 34 premature female infants (104 ± 10 ng/ml sem). During the first year of life, the mean prolactin value for both boys and girls was approximately 10 ng ml. Mean prolactin levels for both male and female children, aged 2–12 years, were approximately 5 ng/ml. Mean levels for the adolescent female were not increased significantly over those for adolescent males. However, the mean prolactin level of all values determined for adult females (7.9 ± 0.40 ng/ml sem) was significantly increased (P < 0.001) over the mean level for adult males (5.2 ± 0.55 ng/ml, sem). Daily serum prolactin throughout the menstrual cycle in six normal female subjects was compared with daily serum HLH levels. Considerable fluctuation was evident, particularly in the luteal phase, where the mean prolactin level was observed to be statistically higher (P < 0.005) than the mean follicular phase level. Insulin hypoglycemia did not produce a significant increase in serum prolactin in 10 normal subjects, whereas arginine infusion produced a twofold increase in mean serum prolactin at 30 min with a return to basal values by 60 min. Glucagon administered intravenously did not produce any significant change in the already elevated levels of prolactin observed on days 1 and 3 of life. Serum prolactin was uniformly and completely suppressed by L-dopa in six subjects for 1–4 hr following a single oral dose of 250 mg. In normal children, the maximal increases in both prolactin and thyroid-stimulating hormone (TSH) were observed at 15–30 min after the intravenous injection of thyrotropin-releasing hormone (TRH) and values were still slightly elevated at 120 min after injection. These studies document the pattern of secretion of serm prolactin from birth to adulthood. The physiologic basis for the increased levels of serum prolactin in the neonate has not been clarified by our studies. Significantly increased levels of prolactin are observed at a time when maximum increases in neonatal breast hypertrophy are observed clinically. Significant mean differences are observed in the adult female population compared with adult males. L-Dopa acts at the hypothalamic level to alter pituitary secretion via alterations in releasing and inhibiting hypothalamic hormones, whereas TRH acts directly on the pituitary. Our studies indicate that responses to these agents in the prepubertal child are qualitatively similar to those in adults. The response of the neonatal hypothalamic pituitary axis to these agents remains to be studied. Speculation: These studies provide a basis for interpretation of disturbances in hypothalamicpituitary regulation of prolactin secretion. Additional studies are required to define the physiologic roles for prolactin in the human during both intrauterine and extrauterine life as well as the normal ontogeny of control mechanisms for prolactin secretion in the neonate and infant. The availability of sufficient purified human prolactin for metabolic balance studies will also be required to enhance our knowledge of this recently isolated human hormone.
TL;DR: In the 23 patients studied, the most consistent disorder of pituitary function proved to be an abnormal response to one or other of the three tests employed for the evaluation of prolactin secretion.
Abstract: Prolactin secretion was assessed in 23 patients with hypothalamic-pituitary disorders using L-Dopa suppression, chlorpromazine (CPZ), and thyrotropin-releasing hormone (TRH) stimulation tests. Based on the responses to these tests, three groups of patients were identified: those with panhypopituitarism (group I) and those with partial hypopituitarism either with (group II) or without (group III) evidence of hypothalamic involvement.
Panhypopituitary patients (group I) consistently had low serum prolactin values and failed to respond to all tests. Patients with hypothalamic involvement (group II) exhibited (a) elevated basal prolactin values. (b) an increase in serum prolactin after TRH stimulation. (c) blunted response to L-Dopa, and (d) lack of response to chlorpromazine stimulation. Patients with partial hypopituitarism but without hypothalamic involvement (group III) had normal serum prolactin levels and suppressed normally after L-Dopa; although the magnitude of response to both stimulatory agents was significantly lower than normally found the ratio of prolactin levels post-CPZ and TRH (Δ prolactin CPZ/Δ prolactin TRH) was similar to the ratio of normal individuals suggesting that these patients (group III) had a normal hypothalamic-pituitary prolactin axis.
In the 23 patients studied, the most consistent disorder of pituitary function proved to be an abnormal response to one or other of the three tests employed for the evaluation of prolactin secretion. Hence these tests have considerable potential as a sensitive screening procedure in the evaluation of patients suspected of having hypothalamic-pituitary disease.
TL;DR: In response to both insulin-induced hypoglycemia and the ingestion of 500 mg.
Abstract: In response to both insulin-induced hypoglycemia and the ingestion of 500 mg. of L-dopa, unipolar depressed patients (most of whom were postmenopausal women) secreted significantly less growth hormone (GH) than did normal subjects or bipolar depressed patients in the same age range (45 to 70 years). Prolactin responses to L-dopa were normal for nearly all subjects. Since it is believed that prolactin responses to L-dopa are mediated by brain dopamine and GH responses by brain norepinephrine, the data tend to support the hypothesis that there is a disturbance of brain norepinephrine metabolism in unipolar depressive illness. However, further study is needed to determine the effects of the menopause on GH secretion.
TL;DR: Results suggest that specific prostaglandins act at the hypothalamus to control pituitary hormone release in ovariectomized rats.
Abstract: Prostaglandin E2 (PGE2) injected into the third ventricle of ovariectomized rats increased plasma luteinizing hormone dramatically and follicle stimulating hormone slightly. PGE1 elevated prolactin; PGF1α or PGF2α had no effect. PGE2 or PGE1 injected directly into the anterior pituitary were ineffective. These results suggest that specific prostaglandins act at the hypothalamus to control pituitary hormone release.