[The risk for osteoporosis in persons treated with thyroid hormones]

Patients taking suppressive doses of thyroid hormones may have adverse effects from such treatment. To test conditions under which such treatment might be deleterious to bone, we studied a group of patients who had undergone thyroidectomy because of thyroid cancer 1 to 21 years previously and were treated with steady suppressive doses of exogenous thyroid hormone. The group consisted from 13 men, 20 premenopausal and 25 postmenopausal women. The level of serum tyroxin a trijodothyronin in average didn't differ from the control subjects; thyreostimulating hormone was significantly lower than in controls. Vertebral bone density (BMD) was significantly reduced and biochemical markers of bone formation and (osteocalcin and bone isoenzyme of alkaline phosphatase in serum) were significantly increased as compared with controls only in postmenopausal patients. Biochemical indices of bone resorption (urinary hydroxyproline and plasma tartrate resistant acid phosphatase activity) were significantly increased in premenopausal and also in postmenopausal women. In thyroid hormone treated women, biochemical indices of both bone resorption and bone formation correlated significantly negatively with serum TSH levels. The results suggest that in postmenopausal women there is no "safe" suppressive dose of thyroid hormone. Patients treated with thyroid hormone should be evaluated for a latent or early symptomatic stage of bone loss. The thyroid drugs used should consist of exact content of thyroid hormones, preferably thyroxin.