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Bone Mass and Osteoporotic Fractures in Hyperthyroid Adults

Authors: Ana Paula Barbosa, Mário Rui Mascarenhas - Endocrinology University Clinic and Environmental Health Institute, Lisbon’s Faculty of Medicine; Fracturary Osteoporosis Outpatient Clinic of the Endocrinology, Diabetes and Metabolism Department, Santa Maria University Hospital, CHLN-EPE, Lisbon, Portugal

Categories: Rheumatology, Traumatology and orthopedics

Sections: Medical forums

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Статья опубликована на с. 84

Overt hyperthyroidism is a clinical condition caused by exaggerated levels of circulating thyroid hormones. Some of its main etiological factors are the hyperfunction of the thyroid gland and the iatrogenic cause, like the ingestion of excessive doses of thyroid hormones.

The potential risks of hyperthyroidism are diverse and can vary from patient to patient; however, heart and bone complications are relatively common, especially among the elderly. Regarding the adult skeleton, several anomalies were described, namely reduced bone mineral density (BMD) and a higher osteoporotic fracture risk. Indeed, hyperthyroidism has been recognized to be an important cause of secondary osteoporosis and a risk factor for hip fracture in women. Moreover, these osteoporotic fractures are associated with a risk of precocious mortality, namely in the elderly.

In adult life, after the acquisition of the peak bone mass, the excess of circulating thyroid hormones can lead to an increase in bone resorption, either by acting directly on osteoclasts or indirectly on osteoblasts. Bone remodeling acce–lerates while the bone formation period is decreased, ori–ginating an incomplete substitution with new bone cells and loss of mineralized bone. Hypercalcemia, hypercalciuria and a negative balance of calcium were also described.

Furthermore, TSH is a negative regulator of bone remodeling, inhibiting the formation, the survival of osteoclasts and the differentiation of osteoblasts. Recent studies have shown that low TSH levels, per se, can lead to osteoporosis and fragility fractures.

In old and young Portuguese patients with endogenous hyperthyroidism, both men and women, significant decreases in the BMD in several skeletal regions and an increase in the prevalence of osteoporosis/low BMD were observed. Moreover, in young Portuguese men with hyperthyroidism, we found a trend for an increase in the prevalence of osteoporotic vertebral fractures detected by VFA.

 



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