Is skeletal responsiveness to thyroid hormone altered in primary osteoporosis or following estrogen replacement therapy?

Suppressing Effect of Free Triiodothyronine on the Negative Association between Body Mass Index and Serum Osteocalcin Levels in Euthyroid Population

Previous studies found that thyroid hormones stimulate osteoblast-like cells to secrete osteocalcin. We aimed to investigate the association between serum thyroid hormone and serum osteocalcin in euthyroid population. The study recruited 1152 community-based euthyroid subjects (average age 59 ± 8 years), among whom 677 were women. Serum free triiodothyronine (FT3), free thyroxine (FT4), thyroid-stimulating hormone (TSH), and osteocalcin were measured by electrochemiluminescence immunoassays. After adjusting for age and gender, partial correlation analysis showed that FT3 and FT3/FT4 were both positively correlated with body mass index (BMI) and serum osteocalcin levels (all P < 0.05) and BMI was negatively correlated with serum osteocalcin levels (P < 0.01), while FT4 and TSH were not correlated with serum osteocalcin levels (all P > 0.05). Age, gender, blood pressure, thyroid hormones, and multiple metabolic risk factors were included in the ridge regression model. FT3 and FT3/FT4 were independently and positively associated with serum osteocalcin levels (all P < 0.05), while BMI was independently and negatively associated with serum osteocalcin levels (P < 0.01). The mediating effect model showed that FT3 and FT3/FT4 suppressed the negative association between BMI and serum osteocalcin levels, with suppressing effects of 6.41% and 10.39%, respectively. In euthyroid subjects, both FT3 and FT3/FT4 were positively associated with serum osteocalcin levels, and they further suppressed the negative association between BMI and serum osteocalcin levels.

N-terminal-pro-B-type natriuretic peptide in acute hyperthyroidism

OBJECTIVE

Serum N-terminal-pro-B-type natriuretic peptide (NT-proBNP) is elevated in systolic heart failure due to volume expansion and pressure overload. Recent data suggest a direct stimulatory effect of thyroid hormones on NT-proBNP synthesis. We examined the influence of acutely induced hyperthyroidism on serum levels of NT-proBNP.

DESIGN

Forty-three healthy women were evaluated before and after treatment with 60 mug triiodothyronine (T(3)) daily for 7 days in a noncontrolled study.

MAIN OUTCOME

Before treatment, NT-proBNP was independently and inversely associated with thyrotropin (TSH), (r = -0.34, p = 0.02). T(3) therapy induced an increase in free T(3) (3.3 times, p < 0.0001) and suppression of TSH ( p < 0.0001). Heart rate increased by 14% ( p < 0.0001); weight decreased 0.6 kg ( p < 0.0001). Median NT-proBNP increased from 53 to 66 pg/mL ( p < 0.0001). The increase in NT-proBNP levels was independently associated with increase in free T(3) ( p = 0.05) and with reduction in TSH ( p = 0.04), without any association to the changes in cardiac workload.

CONCLUSIONS

NT-proBNP is influenced by thyroid function among healthy women, as demonstrated by an inverse association between TSH and NT-proBNP. Induction of an acute hyperthyroid state resulted in an increase in NT-proBNP, which seems to reflect a direct action of T(3) on the NT-proBNP secretion rather than an effect of increased cardiac workload.

Down syndrome and thyroid dysfunction: Should nutritional support be the first-line treatment?

Individuals with Down syndrome (DS) not only have increased risk of hypothyroidism, they also tend to develop a relatively novel mild form of neonatal hypothyroidism. One problem that may predispose those with trisomy 21 to hypothyroidism is the overexpression of the gene DYRK1A, which may have an affect on the thyroid. While thyroxine supplementation (such as Synthroid) is increasingly being advised for those with DS, this treatment may have both positive and negative effects. Nutritional support for hypothyroidism offers some of the same benefits as drug therapy but without the likely negative long-term effects. Early 20th century practitioners used bovine glandulars for those with DS children, which were believed to help support thyroid function. Some doctors in more recent times have also included iodine, L-tyrosine, selenium, and zinc. As nutrition for those with DS has been safely used by some practitioners for many decades, it is suggested that nutritional thyroid support, and not necessarily thyroxine, should be considered for use as a first line treatment for those with trisomy 21. This paper also hypothesizes that nutritional interventions begun prenatally by the mother, may possibly also be of benefit.

Efeito da associação hipertireoidismo-castração no osso de ratas adultas

Foi estudada a relação tireóide-gônadas e sua influência sobre a morfologia óssea de ratas Wistar, com cinco meses de idade, castradas e induzidas ao hipertireoidismo ou mantidas em eutireoidismo por período de 30, 60 e 90 dias. Ratas não castradas foram mantidas nas mesmas condições e serviram como controle. Ao final de cada período, foram determinadas as concentrações plasmáticas de T4 livre, progesterona e estradiol. Os ossos de cada grupo foram submetidos às análises radiológica e histológica. O hipertireoidismo nas ratas não castradas levou à alteração da morfologia do osso, variável ao longo do período experimental, conduzindo, aos 60 dias, à perda de osso trabecular por aumento da reabsorção óssea. Aos 90 dias não houve perda óssea porque o aumento da reabsorção foi acompanhado por maior aposição óssea. Nas ratas eutireóideas castradas, a diminuição dos níveis de progesterona inibiu a aposição óssea, causando, aos 30 dias, pequena perda do osso trabecular das vértebras lombares e do osso alveolar, que se intensificou aos 60 e 90 dias, atingindo também o osso cortical. A administração de tiroxina nas ratas castradas reduziu a osteopenia decorrente da castração aos 60 dias, mas não aos 90 dias, quando a perda óssea foi mais extensa. Conclui-se que o hipoprogesteronismo e o hipoestrogenismo alteram o metabolismo ósseo e que a resposta do osso ao hipertireoidismo depende do perfil plasmático dos esteróides sexuais, do tempo de exposição e da configuração do tecido ósseo.

Relationships existing between the serum cytokine levels and bone mineral density in women in the premenopausal period affected by Graves' disease with subclinical hyperthyroidism

We examined the relationships existing between serum cytokine levels and bone mineral density (BMD) in women of premenopausal age affected by Graves' disease with subclinical hyperthyroidism. The study population consisted of 21 women with untreated hyperthyroid Graves' disease (group H) (age, 36 +/- 2 years), eight women with untreated subclinical hyperthyroid status (group SH) (age, 33 +/- 5 years) and 10 healthy women (group N) (age, 35 +/- 3 years). The following measurements were made in all patients: free T4 (fT4), free T3 (fT3), thyroid stimulating hormone (TSH), TSH receptor antibody (TRab), anti-thyroid peroxidase antibody (anti-TPO), anti-thyroglobulin antibody (anti-Tg), interleukin-2 receptor (IL-2r), interleukin-4 (IL-4), interleukin-8 (IL-8) and interleukin-13 (IL-13). IL-2r and IL-8 levels significantly increased in group H compared with group SH (p < 0.01 and p = 0.05, respectively) and group N (p < 0.001 and p = 0.02, respectively). IL-4 and IL-13 levels tended to be lower in groups H and SH compared with group N, although this difference did not reach statistical significance. Bone mineral density was significantly reduced in only two areas of the femur in group H compared with group N. There was no difference in BMD between groups SH and N. There was no correlation between thyroid hormones, serum cytokine levels and BMD in either group. In conclusion, these results suggest that there were no relationships existing between the serum level of these cytokines and BMD in women of premenopausal age affected by Graves' disease with subclinical hyperthyroidism.

Influência do hipogonadismo na histomorfometria e função tireoidiana de ratas hipotireóideas

Foram investigadas a morfologia e a função tireoidiana de ratas Wistar, adultas, castradas e não castradas e mantidas em estado hipotireóideo pela administração diária de propiltiouracil por 120 dias. Ratas eutireóideas castradas e não castradas serviram de controle. As tireóides, colhidas ao final do experimento, foram pesadas, processadas histologicamente e submetidas à análise morfométrica, pela qual foi determinada a proporção dos componentes glandulares (epitélio folicular, colóide e estroma). No plasma sangüíneo, colhido também ao final do período experimental, foram determinadas as concentrações de T3 total, T4 livre e TSH. O peso e a histomorfometria da tireóide não sofreu influência da castração e o aumento do componente epitelial e decréscimo da quantidade de colóide só foram detectados no hipotireoidismo. No estado eutireóideo a deficiência dos esteróides sexuais levou ao aumento dos valores de T4 livre e T3 total e no hipotireoidismo, exacerbou a queda de T3 total, mas não a de T4 livre. Os valores de TSH não se alteraram em nenhum dos estados funcionais da glândula ou das gônadas. Conclui-se que o hipogonadismo não modifica a hiperplasia glandular e a queda dos níveis plasmáticos de tiroxina livre induzidos pelo propiltiouracil, mas altera profundamente o comportamento da triiodotironina total de acordo com o estado funcional da tireóide, tudo sem alterar os valores plasmáticos de TSH.

Assessment and Recommendations on Factors Contributing to Preanalytical Variability of Urinary Pyridinoline and Deoxypyridinoline

Background: Pyridinoline (PYD) and deoxypyridinoline (DPD) are two of the most extensively characterized biochemical bone markers, but the interpretation of results is hampered by biologic and other preanalytical variability. We reviewed factors contributing to preanalytical variation of pyridinium cross-links in urine.

Methods: We searched four databases for English-language reports on PYD and/or DPD in urine. Searches were restricted to humans, except for studies of stability, when the search was expanded to other species. The 599 identified articles were supplemented with references from those articles and with articles known to the authors.

Results: The mean reported within-day variability was 71% for PYD (range, 57–78%) and 67% for DPD (range, 53–75%). The mean interday variability was 16% for both DPD and PYD (range for PYD, 12–21%; range for DPD, 5–24%). The mean intersubject variabilities across studies were 26% for PYD (range, 12–63%) and 34% for DPD (range, 8–98%) for healthy premenopausal women and 36% (range, 22–61%) and 40%, (range, 27–54%) for postmenopausal women, respectively. Specimen instability and errors in creatinine measurements were additional sources of variability.

Conclusions: Intra- and intersubject variability can be reduced by collecting specimens at a specific time of the day and by maintaining similar patient status at each specimen collection regarding factors such as medications and dietary supplements.

Early postmenopausal bone loss in hyperthyroidism

OBJECTIVES

To evaluate the effect of hyperthyroidism on bone in relation to the menopausal state.

METHODS

Fifty-nine hyperthyroid (HYPER), 40 hypothyroid (HYPO), and 51 control euthyroid (EUTH) women were studied. Bone mineral density (BMD) was assessed by dual X-rays absorptiometry (DXA) at the lumbar spine, and at the femoral neck. A multi-site QUS device evaluated speed of sound (SOS) at the radius (RAD), tibia (TIB), metatarsus (MTR), and phalanx (PLX). Bone markers used were serum bone specific alkaline phosphatase (BSAP) and urinary deoxypyridinoline (DPD).

RESULTS

At all sites, SOS was lower in HYPER than in EUTH (RAD P<0.05, TIB P<0.01, MTR P<0.05, PLX P=0.01). The low SOS was only noted at the early postmenopausal period. BMD at the femoral neck but not at the lumbar spine was lower in HYPER as compared to EUTH (P<0.05). Both femoral neck and tibia were the sites with the highest odds ratio for being hyperthyroid (2.3 and 2.04, respectively). There was no correlation between BMD or SOS and FT(4), TT(3) or duration of hyperthyroidism. BSAP and DPD positively correlated with FT(4) and TT(3) (P<0.05).

CONCLUSIONS

This study suggests that hyperthyroidism affects bone mineralization especially during the early postmenopausal period, and the effect is mainly at the cortical bone.

Biochemical markers of bone turnover in patients with thyroid dysfunctions and in euthyroid controls: a cross-sectional study

Hyperthyroidism is associated with reduced bone mineral density. Conflicting data exist regarding the effects of thyroxine therapy on bone metabolism. The aim of the present study was to assess changes in markers of bone turnover in thyroid dysfunction. A total of 28 patients with overt hyperthyroidism, eight patients with suppressed TSH levels (thyroid hormones within the euthyroid range, no T4 therapy), 25 euthyroid and four hypothyroid patients were included in the present study. Hyperthyroidism resulted in increased bone metabolism, as reflected by increased bone resorption and bone formation parameters. No significant differences in mean levels between patients with TSH supression and those with euthyroidism could be observed; however, a higher frequency of elevated urinary PYD- and DPD excretion rates were noted in patients with TSH suppression. Regression analysis revealed highly significant correlations between bone resorption markers and thyroid parameters, suggesting, that even a mild thyroid hormone excess may lead to an increase in bone resorption. In subjects with suppressed TSH levels and peripheral thyroid hormone levels within the euthyroid range, elevated bone resorption markers point to subclinical hyperthyroidism, if other reasons for an increase in bone turnover rates can be excluded.

Selenoproteins are expressed in fetal human osteoblast-like cells

Selenoproteins are involved in mechanisms of cell differentiation and defense. We investigated the expression of glutathione peroxidases, as well as other selenoproteins, in fetal human osteoblasts (hFOB-cells). Using 75-selenium metabolic labelling of viable hFOB-cells, we identified several selenoproteins in cell lysates of about 45-80 kDa and in the migration range of 14 kDa to 24 kDa. Cells expressed low mRNA levels of both cellular glutathione peroxidase and plasma glutathione peroxidase mRNA as analysed by Southern analysis of RT-PCR products. Basal cellular glutathione peroxidase enzyme activity in hFOB-cells (19.7 nmol NADPH oxidised per min and microg protein) was further increased 2.5-fold by the addition of 100 nM sodium selenite to the culture medium for 3 days. Furthermore, expression of selenoprotein P mRNA was demonstrated by RT-PCR. hFOB-cells did not show activities of the selenoproteins type I or type II 5'-deiodinase. In summary, we identified cellular glutathione peroxidase, plasma glutathione peroxidase and selenoprotein P among of a panel of several 75-selenium labelled proteins in human fetal osteoblasts. The expression of selenoproteins like glutathione peroxidases in hFOB-cells represents a new system of osteoblast antioxidative defense that may be relevant for the protection against hydrogen peroxide produced by osteoclasts during bone remodelling.