THYROID-HORMONE TREATMENT AIMING AT REDUCED, BUT NOT SUPPRESSED, SERUM THYROID-STIMULATING HORMONE LEVELS IN NONTOXIC GOITER - EFFECTS ON BONE METABOLISM AMONGST PREMENOPAUSAL WOMEN

Objectives. To study the effects of six months' treatment with either T4 or T3, aiming at reduced but not totally suppressed serum TSH level s, as measured by a third generation TSH assay, on biochemical bone tu rnover parameters as well as bone mass in patients with nontoxic goitr e. Design. Prospective randomized study with matched control group, no t blinded, Setting. Two University Hospital Clinics in Copenhagen. Sub jects and Intervention. Twenty-four consecutive premenopausal women wi th moderate sized nontoxic goitre. Fourteen patients randomized to T4 or T3 treatment for six months with monthly titration of the dose, aim ing at TSH values between 0.005 and 0.2 mUL(-1). Ten controls. Main ou tcome measures. Serum parathyroid hormone (PTH), serum procollagen I C -terminal propeptide (PICP), serum alkaline phosphatase, serum osteoca lcin, u-pyridinoline, u-deoxypyridinoline, u-hydroxyproline. Bone mass (BMD) at the lumbar spine and at both femoral necks. Results. Serum T SH was generally kept within the desired interval. There was no differ ence in any marker of bone metabolism between the effects of T4 and T3 . Consequently, these groups were combined in order to evaluate the ef fect of thyroid hormones on the bone and mineral metabolism. Thyroid h ormone treatment resulted in increased levels of serum ionized calcium (Ca) (P=0.02), serum alkaline phosphatase (P=0.007), serum-PICP (P=0. 003), serum osteocalcin (P=0.02) and urinary excretion of deoxypridino line (P=0.03) compared to untreated controls. Bone mass did not change . Conclusion. Six months treatment with either T4 or T3 of premenopaus al women with nontoxic goitre, aiming at reduced but not totally suppr essed TSH values, resulted in biochemical signs of increased bone turn over, whereas bone mass remained unaltered, No differences were found between the effects of T4 or T3 treatment.