Treatment of benign nodular goitre with mildly suppressive doses of L-thyroxine: effects on bone mineral density and on nodule size.

Objectives: To evaluate (i) the demineralizing effect of L-thyroxine (LT4) therapy at doses mildly inhibiting serum thyroid stimulating hormone (TSH) in patients with benign nodular goitre; (ii) the efficacy of treatment on nodule size.

Design: Cross-sectional study comparing euthyroid women with nodular goitre treated with LT4 for > or = 2 years (52 +/- 32 months, range 24-138, median 42) and a matched group with untreated goitre.

Subjects: A total of 89 female outpatients (53.3 +/- 9 years; 36 pre- and 53 postmenopausal), 43 treated and 46 untreated.

Main Outcome Measures: Bone mineralization was measured with total body and regional mineralometry [dual energy X-ray absorptiometry (DEXA)], and indirectly evaluated with biochemical parameters (alkaline phosphatase, osteocalcin). Efficacy of LT4 therapy was assessed by measuring the nodule size during ultrasonography. The adequacy of the treatment was evaluated on the basis of serum TSH levels.

Results: No significant differences were found at DEXA for total body and regional mineralization (P > 0.05 for all comparisons) in treated and untreated patients, both in pre- and postmenopausal states. Evaluation of the nodule size during the ultrasound scan showed a reduction of > or = 30% in 11 of 43 treated patients (26%) versus none of the untreated, an unchanged size in 29 treated patients (67%) versus 18 untreated, an increase of nodules and/or new nodule development in three treated patients (7%) versus 28 untreated (61%).

Conclusions: L-thyroxine (LT4) treatment at doses slightly suppressing TSH does not significantly affect bone mineralization, nor does it represent a risk factor for osteoporosis, even in postmenopausal patients. The efficacy of this therapeutic schedule on goitre size is comparable with the effects previously reported with suppressive doses.