The skeleton is an exquisitely sensitive and archetypal T3-target tissue that demonstrates the critical role for thyroid hormones during development, linear growth, and adult bone turnover and maintenance. Thyrotoxicosis is an established cause of secondary osteoporosis, and abnormal thyroid hormone signaling has recently been identified as a novel risk factor for osteoarthritis. Skeletal phenotypes in genetically modified mice have faithfully reproduced genetic disorders in humans, revealing the complex physiological relationship between centrally regulated thyroid status and the peripheral actions of thyroid hormones. Studies in mutant mice also established the paradigm that T3 exerts anabolic actions during growth and catabolic effects on adult bone. Thus, the skeleton represents an ideal physiological system in which to characterize thyroid hormone transport, metabolism, and action during development and adulthood and in response to injury. Future analysis of T3 action in individual skeletal cell lineages will provide new insights into cell-specific molecular mechanisms and may ultimately identify novel therapeutic targets for chronic degenerative diseases such as osteoporosis and osteoarthritis. This review provides a comprehensive analysis of the current state of the art.

Role of Thyroid Hormones in Skeletal Development and Bone Maintenance

The osteoporosis associated with human hyperthyroidism has traditionally been attributed to elevated thyroid hormone levels. There is evidence, however, that thyroid-stimulating hormone (TSH), which is low in most hyperthyroid states, directly affects the skeleton. Importantly, Tshr-knockout mice are osteopenic. In order to determine whether low TSH levels contribute to bone loss in hyperthyroidism, we compared the skeletal phenotypes of wild-type and Tshr-knockout mice that were rendered hyperthyroid. We found that hyperthyroid mice lacking TSHR had greater bone loss and resorption than hyperthyroid wild-type mice, thereby demonstrating that the absence of TSH signaling contributes to bone loss. Further, we identified a TSH-like factor that may confer osteoprotection. These studies suggest that therapeutic suppression of TSH to very low levels may contribute to bone loss in people.

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Hyperthyroid-associated osteoporosis is exacerbated by the loss of TSH signaling

Hashimoto encephalopathy (HE) presents as an encephalopathy without central nervous system infection or tumor. HE is associated with autoimmune thyroiditis and is thus considered to be an autoimmune disorder. The prevalence of HE is low, but death and status epilepticus have been reported. HE manifests with a wide range of symptoms that include behavioral changes and confusion. Elevated thyroid antibodies are present in the majority of cases and are required for the diagnosis of HE. Normal brain MRI findings are found in the majority of patients diagnosed with HE. The most consistent CSF abnormality noted in HE patients is the presence of elevated protein. Most HE patients respond well to steroid therapy. Clinical improvements are also observed with IV immunoglobulin and plasmapheresis. In conclusion, it is now generally accepted that the diagnosis of HE must include encephalopathy characterized by cognitive impairment associated with psychiatric features, such as hallucinations, delusions, and paranoia. Autoimmune encephalitis and prion disease should be considered in the differential diagnosis due to the similarity of the clinical features of these conditions to those of HE.

Hashimoto encephalopathy: literature review.

Hashimoto's encephalopathy: A rare proteiform disorder.

The impacts of organochlorines and other persistent pollutants on thyroid and metabolic health.

Recently, several patients have been reported with various signs of encephalopathy and high thyroid antibody levels together with good responsiveness to glucocorticoid therapy. Despite the various clinical presentations, these cases have been termed "Hashimoto encephalopathy" (HE). Although all of the pathogenic components have not yet been clearly elucidated, it is believed that brain vasculitis and autoimmunity directed against common brain-thyroid antigens represent the most likely etiologic pathway. The most common clinical signs include unexplained or epilepsy-like seizures resistant to anti-convulsive treatment, confusion, headaches, hallucinations, stroke-like episodes, coma, impairment of cognitive function, behavioral and mood disturbance, focal neurological deficits, disturbance of consciousness, ataxia, and presenile dementia, together with the presence of high thyroid antibody levels, especially against thyroperoxidase (TPOab). In most cases, the thyroid function is normal or decreased; the thyroid function is rarely increased. The examination of the cerebrospinal fluid, EEG, MRI, SPECT, and neuropsychological examinations are primarily used as diagnostic tools. Most cases showed neural symptoms for months before the acute onset; in some cases, a dramatic acute onset was described. Once the diagnosis is made, corticosteroid treatment usually provides a dramatic recovery. The authors also present a short review of literary cases reported in last decade.

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Hashimoto Encephalopathy: A Rare Intricate Syndrome

OBJECTIVE Since the positive role of thyrotropin (TSH) in bone remodeling has been recently emphasized, this cross-section study is aimed to evaluate the association of bone status with the level of TSH and free thyroxine (FT4) in the cohort of postmenopausal women after long-term treatment of thyroid disorders and age matched controls. METHODS Urinary calcium (dUCa) and serum level of TSH, FT4 and of bone turnover markers (BTMs) such as alkaline phosphatase (ALP), osteocalcin (OC), cross linked N-telopeptide of type 1 collagen (NTx) as well as lumbar spine L 1-4 (BMD-L) and femoral hip (BMD-F) mineral density were determined in 113 postmenopausal women consisting of 42 patients with Graves disease treated by carbimazole, 32 patients with thyroid cancer treated with L-thyroxine and 39 age matched women without any thyroid and osteological disorders. For statistical evaluation t-test, Pearson's correlation coefficient and linear multiple regression were used. RESULTS To compare the association of TSH versus FT4 with BMD and BTMs the pooled cohort of all 113 women was divided in two groups in terms of TSH level: 1. 34 women with low TSH (>or=0.50 mU/l); 2. 79 women with normal TSH (0.51-4.3 mU/l). In spite of significantly higher FT4 level, the Group 2 with normal TSH level had significantly higher BMD-L and BMD-F (p<0.001) and, in contrast, significantly lower urinary dUCa, ALP, OC (all at p<0.001) and NTx (p<0.01) as compared to the Group 1 with low TSH level. Linear multiple regression showed highly significant influence of TSH on BMD-L and BMD-F0 (p<0.001) independent of age, FT4 and body mass index, while that of FT4 was not significant. The strength of linear interrelation between all variables used was finally tested by Pearson's correlation coefficient (Table 3) which was highly positive for TSH with BMD-F and BMD-L, but highly negative for TSH with serum NTx, OC, ALP) and urinary calcium (dUCa). In contrast, no significant correlation was found between the level of FT4 and BMD. CONCLUSIONS Irrespectively of FT4 level, postmenopausal women with normal TSH level showed a favorable bone status as compared to these with low level of TSH which is consistent with the view that TSH itself possibly participates in playing a favorable role in influencing the bone mineral density in adult women.

The level of TSH appeared favourable in maintaining bone mineral density in postmenopausal women.

OBJECTIVE: This cross-sectional study aimed to evaluate the interrelations between endogenous TSH level on one side and the status of bone mineral density (BMD) and bone metabolic turnover (BMT) on the other in pooled four groups of premenopausal women either without or with a long-term L-thyroxine treatment. METHODS: Serum levels of free thyroxine (FT4), thyrotropin (TSH), calcium (Ca), alkaline phosphatase (ALP), osteocalcin OC) and cross linked N-telopeptide of type 1 collagen (NTx) as well as urinary calcium (U-Ca/24h), bone mineral density of lumbar spine L 1-4 (BMD-L) and femoral hip (BMD-F) were estimated in a cohort of 151 premenopausal women (median 36 years) consisting of four groups: Group 1, 40 healthy untreated women, while three other groups consisted of patients previously treated for about 5 years; Group 2, 41 patients with genuine hypothyroidism treated by L-thyroxine (50-100 microg daily); Group 3, 40 patients with genuine hyperthyroidism treated by Carbimazol (10-15 mg daily); Group 4, 30 patients treated by suppressive doses of L-thyroxine (100-150 microg daily) after thyroidectomy for thyroid cancer (n=10) or because of progressively growing benign goitre (n=20). RESULTS: When using multiple correlation analysis (Pearson's r) in pooled 151 women, TSH showed significant positive correlation with BMD-L (p<0.01) and BMD-F (p<0.001) and, at the same time, significant negative correlation with serum level of BMT markers such as ALP (p<0.05), OC (p<0.05) and NTx (p<0.01), while the correlation of FT4 with BMD-L, BMD-F was significantly negative (p<0.001 for both) and that with all BMT markers was significantly positive (p<0.05 to <0.001). Thus, it appeared that higher TSH level was associated with increased bone mineral density and, at the same, with decreased bone metabolic turnover. These interrelations were further supported by the findings of significantly lower BMD-F (p<0.01), BMD-L (p<0.001) and significantly higher ALP, OC and NTX (all at p<0.001) in the group of 36 women with TSH level<0.3 mU/l as compared to the group of 115 women with TSH level range of 0.35-6.3 mU/l). CONCLUSIONS: Irrespectively of thyroid diagnosis and/or previous long term thyroxine treatment in some groups, this cross sectional study showed that, after the pooled group of 151 women has been redistributed according to the actual TSH level, the bone mineral density and the level of bone turnover markers was significantly more favorable in 115 subjects with TSH level range of 0.35-6.3 mU/l than these in 36 women with TSH<0.3 mU/l.

Thyrotropin versus thyroid hormone in regulating bone density and turnover in premenopausal women.

Hashimoto's encephalopathy and rare cases of hyperthyroidism (review and case report).

OBJECTIVES Because of well known association between the exposure to persistent organochlorinated pollutants (POPs) and impaired immune system, it was attempted to check possible coincidence of nuclear and thyroperoxidase antibodies with the levels of major POPs. METHODS Antinuclear antibodies. (ANA) were estimated by indirect immunofluorescence test using Hep2- cells and thyroperoxidase antibodies (TPOab) by electrochemiluminiscent immunoassay in the cohort of 253 adults (82 males and 171 females) aged 21-75 years, among them 144 (46 males and 98 females) from the area polluted (POLL) by polychlorinated biphenyls (PCB) and 109 (36 males and 73 females) from the area of background pollutrion (BCGR). In the same cohort fifteen congeners of PCB and also total DDE (2,2'-bis(4-chlorophenyl)-1,1-dichloroethylene) and hexachlorobenzene (HCB) were estimated by high resolution gas chromatography/mass spectrometry. RESULTS Prevalence of ANA only was significantly higher in POLL than in BCGR in males (p < 0.001) and females (p < 0.001) and the same was true for the prevalence of TPOab in males (p < 0.05) and females (p < 0.01) from POLL. In addition, also the prevalence of coincident ANA+TPOab in males (p < 0.001) and females (p < 0.05) was significantly higher in POLL. In a total of 253 pooled males and females from both areas and stratified in terms of PCB level quintiles. The prevalence of ANA in the 4th and 5th quintile of each among three pollutants (PCB, DDE and HCB) was significantly higher (p < 0.01 or < 0.001) and showed the parallel increase with the level of all pollutants. CONCLUSIONS Significantly increased prevalence of ANA either only or in coincidence with TPOab was found related to increasing level of PCB, DDE and HCB.

Increased prevalence and coincidence of antinuclear and antithyroid antibodies in the population exposed to high levels of polychlorinated pollutants cocktail.

P Langer

Papers

Hashimoto Encephalopathy: A Rare Intricate Syndrome

The level of TSH appeared favourable in maintaining bone mineral density in postmenopausal women.

Thyrotropin versus thyroid hormone in regulating bone density and turnover in premenopausal women.

Hashimoto's encephalopathy and rare cases of hyperthyroidism (review and case report).

Increased prevalence and coincidence of antinuclear and antithyroid antibodies in the population exposed to high levels of polychlorinated pollutants cocktail.