TR expression and function in human bone marrow stromal and osteoblast-like cells

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.

Disruption of BMP Signaling Prevents Hyperthyroidism-Induced Bone Loss in Male Mice

Thyroid hormones (TH) are key regulators of bone health, and TH excess in mice causes high bone turnover-mediated bone loss. However, the underlying molecular mechanisms of TH actions on bone remain poorly defined. Here, we tested the hypothesis whether TH mediate their effects via the pro-osteogenic bone morphogenetic protein (BMP) signaling pathway in vitro and in vivo. Primary murine osteoblasts treated with 3,3',5-triiodo-L-thyronine (T₃ ) showed an enhanced differentiation potential, which was associated with activated canonical BMP/SMAD signaling reflected by SMAD1/5/8 phosphorylation. Blocking BMP signaling at the receptor (LDN193189) and ligand level (noggin, anti-BMP2/BMP4 neutralizing antibodies) inhibited T₃ -induced osteogenic differentiation. In vivo, TH excess over 4 weeks in male C57BL/6JRj mice led to severe trabecular bone loss with a high bone turnover that was completely prevented by treatment with the BMP ligand scavenger ALK3-Fc. Thus, TH activate the canonical BMP pathway in osteoblasts to promote their differentiation and function. Importantly, this study indicates that blocking the BMP pathway may be an effective strategy to treat hyperthyroidism-induced bone loss. © 2020 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.

Lack of the Thyroid Hormone Transporter Mct8 in Osteoblast and Osteoclast Progenitors Increases Trabecular Bone in Male Mice

Background: Bone is an important target of thyroid hormones (THs), which require transport into target cells to exert their actions. Recently, the TH-specific monocarboxylate transporter 8 (Mct8) was reported as a regulator of bone mass in male mice. However, its global deletion leads to high 3,3',5-L-triiodothyronine (T3) serum concentrations that may mask direct effects of Mct8-deficiency on bone. In this study, we assessed the bone cell intrinsic function of Mct8 ex vivo and in vivo using conditional Mct8-knockout lines specifically targeting osteoclast and osteoblast progenitors, as well as mature osteoblasts and osteocytes. Materials and Methods: Twelve-week-old male mice with a global Mct8-deficiency or a conditional Mct8-knockout in osteoclast precursors, osteoprogenitors, or mature osteoblasts/osteocytes were analyzed regarding their bone microarchitecture, turnover, and strength. Furthermore, ex vivo studies were conducted to investigate the role of Mct8 in bone cell differentiation and functionality, as well as TH uptake. Results: Global Mct8-knockout mice demonstrated 1.7-fold higher T3 serum concentrations and trabecular bone loss (-28%) likely due to an increased bone turnover as shown by increased osteoblast (+45%) and osteoclast numbers (+41%). However, cortical bone mineral density was increased. Ex vivo cultures of bone marrow-derived osteoblasts and osteoclasts revealed highest expression of Mct8 in mature bone cells. In addition, Mct8-deficiency resulted in a lower mRNA expression of osteoblast and osteoclast differentiation markers, as well as a reduced mineralization capacity and osteoclast numbers, respectively, indicating a bone cell intrinsic role of Mct8. In fact, conditional Mct8-knockout and inhibition of Mct8 in osteoblasts led to an attenuated T3 uptake ex vivo. In vivo, osteoprogenitor-specific Mct8-knockout enhanced trabecular bone volume (+16%) with osteoblast numbers being increased 3.7 fold. Interestingly, Mct8-deficiency in osteoprogenitors and late osteoblasts/osteocytes both resulted in cortical bone loss. Finally, Mct8-deletion in osteoclast progenitors increased trabecular bone volume (+20%) due to reduced osteoclast numbers (-32%), whereas osteoblast numbers were enhanced (+25%). Conclusions: This study confirms that high systemic T3 in global Mct8-knockout mice masks the direct effect of Mct8. Moreover, it identifies Mct8 as a critical regulator of trabecular vs. cortical bone by regulating T3 uptake and highlights its cell intrinsic role in osteoclast and osteoblast progenitors.

Thyroid Hormone Actions and Bone Remodeling – The Role of the Wnt Signaling Pathway

Thyroid hormones are indispensable for bone development and growth. Also in adults, bone mass maintenance is under the control of thyroid hormones. Preclinical and clinical studies established untreated hyperthyroidism as a cause for secondary osteoporosis with increased fracture risk. Thus, normal thyroid function is essential for bone health. Mechanistically, thyroid hormone excess accelerates bone turnover with predominant bone resorption. How thyroid hormones affect osteoblast and osteoclast functions, however, still remains ill-defined. The Wnt signaling pathway is a major determinant of bone mass and strength as it promotes osteoblastogenesis and bone formation, while inhibiting bone resorption. So far, only few studies investigated a possible link between thyroid hormones, bone metabolism and the Wnt pathway. In this review, we summarize the literature linking thyroid hormones to bone homeostasis through Wnt signaling and discuss its potential as a therapeutic approach to treat hyperthyroidism-induced bone loss.

The Role of Dickkopf-1 in Thyroid Hormone-Induced Changes of Bone Remodeling in Male Mice

Thyroid hormones regulate bone homeostasis, and exogenously induced hyperthyroidism and hypothyroidism in mice was recently found to be associated with an altered expression of the Wnt inhibitor Dickkopf-1 (Dkk1), a determinant of bone mass. Here, we assessed the role of Dkk1 in thyroid hormone-induced changes in bone using conditional Dkk1 knockout mice. Male mice with a global (Dkk1fl/fl;Rosa26-CreERT2) or osteocyte-specific (Dkk1fl/fl;Dmp1:Cre) deletion of Dkk1 were pharmacologically rendered hypothyroid or hyperthyroid. The bone phenotype was analyzed using micro-CT analysis, dynamic histomorphometry, and serum concentrations of bone turnover markers. Hypothyroid and hyperthyroid Cre-negative mice of either Cre line revealed the expected changes in bone volume with hypothyroid mice displaying a 40% to 60% increase in vertebral trabecular bone volume, while hyperthyroid mice lost 45% to 60% of bone volume. Similar changes were observed at the spine. Interestingly, Cre-positive mice of both lines did not gain or lose as much bone at the femur when rendered hypothyroid or hyperthyroid. While Cre-negative hypothyroid mice gained 80% to 100% bone volume, Cre-positive hypothyroid mice only increased their bone volume by 55% to 90%. Similarly, Cre-negative hyperthyroid mice lost 74% to 79% bone, while Cre-positive hyperthyroid mice merely lost 40% to 54%. Despite these site-specific differences, both global and osteocyte-specific Dkk1 knockout mice displayed similar changes in bone turnover as their Cre-negative controls in the hypothyroid and hyperthyroid states. While osteoblast and osteoclast parameters were increased in hyperthyroidism, hypothyroidism potently suppressed bone cell activities. Loss of Dkk1 is not sufficient to fully reverse thyroid hormone-induced changes in bone mass and bone turnover.

The phytoestrogen genistein prevents trabecular bone loss and affects thyroid follicular cells in a male rat model of osteoporosis

As a major phytoestrogen of soy, genistein effectively prevents bone loss in both humans and rat models of osteoporosis. However, although the bone-sparing effects of genistein are achieved directly through estrogen receptors, its mode of action on bone by modulation of other endocrine functions is not entirely clear. Thus, thyroid hormones and calcitonin (CT) have an essential influence on bone metabolism. Besides its action on bones, in this study we examined the effect of genistein on the activity of two different endocrine cell populations, thyroid follicular and C-cells. Fifteen-month-old Wistar rats were either bilaterally orchidectomized (Orx) or sham-operated (SO). Two weeks after surgery, half of the Orx rats were treated chronically with 30 mg kg^-1 b.w. genistein (Orx + G) subcutaneously (s.c.) every day for 3 weeks, while the remaining Orx rats and the SO rats were given the same volume of sterile olive oil to serve as controls. For histomorphometrical analysis of the trabecular bone microarchitecture an ImageJ public domain image processing programme was used. Thyroid sections were analysed histologically and stereologically after visualization of follicular and C-cells by immunohistochemical staining for thyroglobulin and CT. Thyroid follicular epithelium, interstitium, colloid and CT-immunopositive C-cells were examined morphometrically. Serum concentrations of osteocalcin (OC), triiodothyronine (T₃ ), thyroxine (T₄ ) and CT were determined as well as urinary calcium (Ca²⁺ ) concentrations. Genistein treatment significantly increased cancellous bone area (B.Ar), trabecular thickness (TbTh) and trabecular number (TbN) (P < 0.05), but trabecular separation (Tb.Sp) was decreased (P < 0.05) compared with control Orx rats. In the thyroid, genistein treatment significantly elevated the relative volume density (Vv) of the follicular cells (P < 0.05) compared with Orx, whereas Vv of the colloid was lower (P < 0.05) than in the Orx. Evaluation of the biochemical parameters showed significant reductions in serum OC, T₃ , T₄ and urinary Ca²⁺ concentrations (P < 0.05), compared with Orx rats. These data indicate that genistein treatment improves the trabecular microarchitecture of proximal tibia, induces histomorphometrical changes in thyroid glands, and decreases circulating thyroid hormone levels in orchidectomized rat model of male osteoporosis.

Dose-dependent effect of triiodothyronine on the chondrogenic differentiation of mesenchymal stem cells from the bone marrow of female rats

OBJECTIVES

Verify the in-vitro effect of triiodothyronine (T3) on the chondrogenic differentiation of female rat bone marrow mesenchymal stem cells (BMMSCs) over several time periods and at several doses.

METHODS

CD54 + /CD73 + /CD90 +  BMMSCs from Wistar female rats were cultured in chondrogenic medium with or without T3 (0.01; 1; 100; 1000 nm). At seven, 14 and 21 days, the cell morphology, chondrogenic matrix formation and expression of Sox9 and collagen II were evaluated.

KEY FINDINGS

The dose of 100 nm did not alter the parameters evaluated in any of the periods studied. However, the 0.01 nm T3 dose improved the chondrogenic potential by increasing the chondrogenic matrix formation and expression of Sox9 and collagen II in at least one of the evaluated periods; the 1 nm T3 dose also improved the chondrogenic potential by increasing the chondrogenic matrix formation and the expression of collagen II in at least one of the evaluated periods. The 1000 nm T3 dose improved the chondrogenic potential by increasing the chondrogenic matrix formation and Sox9 expression in at least one of the evaluated periods.

CONCLUSIONS

T3 has a dose-dependent effect on the differentiation of BMMSCs from female rats.

Sclerostin Blockade and Zoledronic Acid Improve Bone Mass and Strength in Male Mice With Exogenous Hyperthyroidism

Hyperthyroidism in mice is associated with low bone mass, high bone turnover, and high concentrations of sclerostin, a potent Wnt inhibitor. Here, we explored the effects of either increasing bone formation with sclerostin antibodies (Scl-Ab) or reducing bone turnover with bisphosphonates on bone mass and strength in hyperthyroid mice. Twelve-week-old C57BL/6 male mice were rendered hyperthyroid using l-thyroxine (T4; 1.2 µg/mL added to the drinking water) and treated with 20 mg/kg Scl-Ab twice weekly or 100 µg/kg zoledronic acid (ZOL) once weekly or phosphate-buffered saline for 4 weeks. Hyperthyroid mice displayed a lower trabecular bone volume at the spine (-42%, P < 0.05) and the distal femur (-55%, P < 0.05) compared with euthyroid controls. Scl-Ab and ZOL treatment of hyperthyroid mice increased trabecular bone volume at the spine by threefold and twofold, respectively. Serum bone formation and resorption markers were increased in hyperthyroid mice and suppressed by treatment with ZOL but not Scl-Ab. Trabecular bone stiffness at the lumbar vertebra was 63% lower in hyperthyroid mice (P < 0.05) and was increased fourfold by Sci-Ab (P < 0.001) and threefold by ZOL treatment (P < 0.01). Bone strength based on ultimate load, which was 10% lower in hyperthyroidism, was increased by Scl-Ab by 71% and ZOL by 22% (both P < 0.001). Increased proportion of low mineralized bone seen in hyperthyroid mice was restored by treatment with Scl-Ab and ZOL. Thus, bone-forming and antiresorptive drugs prevent bone loss in hyperthyroid mice via different mechanisms.

Role of Thyroid Hormones in Skeletal Development and Bone Maintenance

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.

Comparative study of osteogenic differentiation potential of mesenchymal stem cells derived from bone marrow and adipose tissue of osteoporotic female rats

Osteoporosis causes reduction of osteogenic differentiation of mesenchymal stem cells (MSCs) from bone marrow and adipose tissue. This study was designed to compare the osteogenic potential of bone marrow mesenchymal stem cells (BMMSCs) and adipose-derived stem cells (ADSCs) of ovariectomized (OVX) rats. MSC were harvested from bone marrow and inguinal fat pads of six OVX rats. The limitations of this report are that cells from different animals were pooled for the purpose of the experiments that were carried out in this study. At 7, 14 and 21 d of osteogenic differentiation, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) conversion, alkaline phosphatase activity and gene expression for collagen I, osteocalcin, bone sialoprotein, osteopontin and bone morphogenetic protein-2 bone morphogenetic protein-2 (BMP-2) were analyzed. At 21 d, percentage of cells per field and percentage of mineralized nodule were analyzed. The data were subjected to analysis of variance, and the means were compared by Student-Newman-Keuls test. The cells, regardless of group, showed phenotypic characteristics consistent with stem cells. MTT conversion, alkaline phosphatase activity, percentage of mineralized nodule and expression of collagen I, osteocalcin and BMP-2 of ADSCs from OVX rats were higher when compared to BMMSCs from OVX rats in at least one of the evaluated periods (p<0.05). However, bone sialoprotein and osteopontin expression were smaller than those observed in BMMSCs for all evaluated periods (p<0.05). It was concluded that the ADSCs from OVX rats have higher osteogenic potential when compared to BMMSCs from OVX rats. This result suggests that the treatment of osteoporosis with autologous ADSCs may be more efficient.

Excess TSH causes abnormal skeletal development in young mice with hypothyroidism via suppressive effects on the growth plate

Hypothyroidism in the young leads to irreversible growth failure. hyt/hyt Mice have a nonfunctional TSH receptor (TSHR) and are severely hypothyroid, but growth retardation was not observed in adult mice. We found that epiphysial cartilage as well as cultured chondrocytes expressed functional TSHR at levels comparable to that seen in the thyroid, and that addition of TSH to cultured chondrocytes suppressed expression of chondrocyte differentiation marker genes such as Sox-9 and type IIa collagen. Next, we compared the long bone phenotypes of two distinct mouse models of hypothyroidism: thyroidectomized (THYx) mice and hyt/hyt mice. Although both THYx and hyt/hyt mice were severely hypothyroid and had similar serum Ca(2+) and growth hormone levels, the tibia was shorter and the proliferating and hypertrophic zones in the growth plate was significantly narrower in THYx mice than in hyt/hyt mice. Supplementation of hyt/hyt mice thyroid hormone resulted in a wider growth plate compared with that of wild-type mice. Expressions of chondrocyte differentiation marker genes Sox-9 and type IIa collagen in growth plate from THYx mice were 52 and 60% lower than those of hyt/hyt mice, respectively. High serum TSH causes abnormal skeletal development in young mice with hypothyroidism via suppressive effects on the growth plate.

Thyroid hormone actions in cartilage and bone

Thyroid hormones exert widespread and complex actions in almost all tissues during development, throughout childhood and in adults. The skeleton is an important T3-target tissue that exemplifies these processes, and yet understanding of the specific cellular and molecular mechanisms of T3 action in bone and cartilage remains incomplete. Here, the skeleton is considered as a T3-target tissue. The actions of thyroid hormones during skeletal development and in chondrocytes and growth plate cartilage during post-natal linear growth are outlined. The physiological importance of these actions are discussed in relation to patients with autosomal dominant mutations in genes encoding the thyroid hormone receptors TRα1 and TRβ, and in mice harbouring deletions or mutations of the orthologous genes. The role of thyroid hormones and the control of T3 action in bone turnover and maintenance are also outlined, and T3 action in bone-forming osteoblasts and bone-resorbing osteoclasts discussed. The physiological and functional consequences of T3 action in bone are considered in relation to mutant mouse models and to effects on bone mineral density and fracture susceptibility in humans. Finally, new studies identifying a putative role for thyroid hormone metabolism in articular cartilage maintenance and the pathogenesis of osteoarthritis are considered. The pharmacological context of these new findings is discussed, emphasising the importance of this emerging field of study in thyroid hormone pathophysiology.

Thyroid hormone (T3)-induced up-regulation of voltage-activated sodium current in cultured postnatal hippocampal neurons requires secretion of soluble factors from glial cells

We have previously shown that treatment with the thyroid hormone T(3) increases the voltage-gated Na(+)current density (Nav-D) in hippocampal neurons from postnatal rats, leading to accelerated action potential upstrokes and increased firing frequencies. Here we show that the Na(+) current regulation depends on the presence of glial cells, which secrete a heat-instable soluble factor upon stimulation with T(3). The effect of conditioned medium from T(3)-treated glial cells was mimicked by basic fibroblast growth factor (bFGF), known to be released from cerebellar glial cells after T(3) treatment. Neutralization assays of astrocyte-conditioned media with anti-bFGF antibody inhibited the regulation of the Nav-D by T(3). This suggests that the up-regulation of the neuronal sodium current density by T(3) is not a direct effect but involves bFGF release and satellite cells. Thus glial cells can modulate neuronal excitability via secretion of paracrinely acting factors.

Histomorfometria óssea de ratas hipertireóideas lactantes e não-lactantes

O objetivo deste estudo foi verificar se o hipertireoidismo potencializa a osteopenia causada pela lactação. Foram utilizadas 24 ratas adultas distribuídas em quatro grupos: eutireóideo não lactante (controle), eutireóideo lactante, hipertireóideo não-lactante e hipertireóideo lactante. Todos os animais foram necropsiados, 20 dias após a gestação. As vértebras torácicas e lombares, o fêmur e a tíbia foram colhidos, descalcificados e submetidos à análise histomorfométrica. O grupo eutireóideo lactante apresentou osteopenia intensa em todos os sítios ósseos estudados. No grupo hipertireóideo não-lactante, não houve alteração da porcentagem de tecido ósseo trabecular nos sítios analisados. No grupo hipertireóideo lactante, havia osteopenia na tíbia e no fêmur, semelhante à do grupo eutireóideo lactante. Mas a porcentagem de tecido ósseo trabecular em todos os corpos vertebrais foi significativamente maior em comparação ao grupo eutireóideo lactante. Conclui-se que o hipertireoidismo não agrava a osteopenia lactacional em ratas, mas minimiza a osteopenia vertebral por estimular a atividade osteoblástica.

Influence of hormones on osteogenic differentiation processes of mesenchymal stem cells

Bone development, regeneration and maintenance are governed by osteogenic differentiation processes from mesenchymal stem cells through to mature bone cells, which are directed by local growth and differentiation factors and modulated strongly by hormones. Mesenchymal stem cells develop from both mesoderm and neural crest and can give rise to development, regeneration and maintenance of mesenchymal tissues, such as bone, cartilage, muscle, tendons and discs. There are only limited data regarding the effects of hormones on early events, such as regulation of stemness and maintenance of the mesenchymal stem cell pool. Hormones, such as estrogens, vitamin D-hormone and parathyroid hormone, besides others, are important modulators of osteogenic differentiation processes and bone formation, starting off with fate decision and the development of osteogenic offspring from mesenchymal stem cells, which end up in osteoblasts and osteocytes. Hormones are involved in fetal bone development and regeneration and, in childhood, adolescence and adulthood, they control adaptive needs for growth and reproduction, nutrition, physical power and crisis adaptation. As in other tissues, aging in mesenchymal stem cells and their osteogenic offspring is accompanied by the accumulation of genomic and proteomic damage caused by oxidative burden and insufficient repair. Failsafe programs, such as apoptosis and cellular senescence avoid tumorigenesis. Hormones can influence the pace of such events, thus supporting the quality of tissue regeneration in aging organisms in vivo; for example, by delaying osteoporosis development. The potential for hormones in systemic therapeutic strategies is well appreciated and some concepts are approved for clinical use already. Their potential for cell-based therapeutic strategies for tissue regeneration is probably underestimated and could enhance the quality of tissue-engineering constructs for transplantation and the concept of in situ-guided tissue regeneration.

A thyrotoxic skeletal phenotype of advanced bone formation in mice with resistance to thyroid hormone

Thyroid hormone (T3) regulates bone turnover and mineralization in adults and is essential for skeletal development during childhood. Hyperthyroidism is an established risk factor for osteoporosis. Nevertheless, T3 actions in bone remain poorly understood. Patients with resistance to thyroid hormone, due to mutations of the T3-receptor beta (TRbeta) gene, display variable phenotypic abnormalities, particularly in the skeleton. To investigate the actions of T3 during bone development, we characterized the skeleton in TRbetaPV mutant mice. TRbetaPV mice harbor a targeted resistance to thyroid hormone mutation in TRbeta and recapitulate the human condition. A severe phenotype, which includes shortened body length, was evident in homozygous TRbetaPV/PV animals. Accelerated growth in utero was associated with advanced endochondral and intramembranous ossification. Advanced bone formation resulted in postnatal growth retardation, premature quiescence of the growth plates, and shortened bone length, together with increased bone mineralization and craniosynostosis. In situ hybridization demonstrated increased expression of fibroblast growth factor receptor-1, a T3-regulated gene in bone, in TRbetaPV/PV perichondrium, growth plate chondrocytes, and osteoblasts. Thus, the skeleton in TRbetaPV/PV mice is thyrotoxic and displays phenotypic features typical of juvenile hyperthyroidism.

A osteoporose e os distúrbios endócrinos da tireóide e das gônadas

Apesar da dedicação incessante dos pesquisadores no estudo da osteoporose, muito ainda necessita ser elucidado. A deficiência dos esteróides sexuais, principalmente a de estrógeno, é considerada a principal causa de osteoporose, embora existam inúmeros outros fatores envolvidos. O hipertireoidismo, por exemplo, é considerado um dos fatores de risco para indução ou agravamento da osteoporose e tem despertado o interesse para o estudo dos efeitos de T3 e T4 sobre o metabolismo ósseo. Embora o hipotireoidismo e a afuncionalidade das gônadas seja uma associação freqüente na mulher, a hipofunção da tireóide não é considerada fator de risco para a osteoporose da menopausa. Assim, o estudo da inter-relação entre os distúrbios endócrinos, tão comuns na idade avançada, e a osteoporose é fundamental, pois deste conhecimento poderão advir meios de controle e tratamento adequados, bem como a definição da real natureza do distúrbio ósseo. O objetivo desta revisão é apresentar e discutir alguns aspectos da osteoporose e sua inter-relação com os distúrbios endócrinos da tireóide e das gônadas.