Bone metabolism in premenopausal women with nontoxic goiter and reduced serum thyrotropin levels.

Objective: To study whether premenopausal women with nontoxic goiter, but reduced serum TSH as a sign of spontaneous subclinical hyperthyroidism have decreased bone mass or other indications of increased bone turnover.

Design and subjects: In a cross-sectional study, bone mass measurements were performed in the distal forearm and the lumbar spine in 11 premenopausal women with nontoxic goiter and a stable reduction in serum TSH (median (range) 8 months (6-108 months)), and in 22 matched controls. In a longitudinal study, measurements were repeated every 3 months for a maximum period of 2 years in 9 of the patients (6 completed 9 months, 4 completed 2 years follow-up).

Results: Serum TSH in the patients were (median (range)) 0.025 mU/l (< 0.005-0.256 mU/l). Patients had a bone mineral content of the distal forearm and a bone mineral density of the lumbar spine similar to those of controls, medians of controls: 98.4% and 93.8%, respectively. The risk of a type 2 error for over-looking a 10% difference was 2% for the distal forearm and 20% for the spine. TSH correlated negatively with marginal significance (p < 0.10) with markers of bone turnover: plasma osteocalcin, serum alkaline phosphatase, and fasting urinary hydroxyproline corrected for creatinine, although all patients had absolute values of these parameters within normal range. During follow-up bone mass measurements did not tend to decrease, but serum alkaline phosphatase and fasting urinary hydroxyproline showed increasing trends (p < 0.05).

Conclusions: Premenopausal women with nontoxic goiter and reduced serum TSH do not seem to have reduced bone mass but seem to demonstrate signs of increased bone turnover.