Endocrine Abstracts

Objectives: To determine the effect on bone mineral density (BMD) of the sub clinical hyperthyroidism (SH) due to TSH-suppressive treatment with levothyroxine after thyroidectomy in men with differentiated thyroid carcinoma (DTC).

Materials and methods: Cross-sectional and retrospective study in 32 men (56±14 years) treated with levothyroxine for a minimum of 5 years, with TSH concentrations <0.05 mUI/ml and normal T3 levels in all determinations performed every 3–6 months during the follow-up. The control group included 32 men matched for age and body mass index. Exclusion criteria: patients under treatment or diseases that could interfere with the BMD.

Determinations: TSH, T4L, T3, calcium, alkaline phosphatase, PTH, vitamin D, testosterone, urinary calcium excretion in 24h and urine N-terminal telopeptides of type I collagen. BMD was measured by DEXA (proximal femur, distal radium and lumbar spine). Calcium intake, physical activity, toxic habits and history of bone fractures were collected using a questionnaire.

Results: Duration of levothyroxine treatment: 15±5 years. Dose: 2.6±0.7 mcg/kg per 24 h. There were no significant differences in anthropometric data, physical activity, unhealthy habits or calcium intake between patients and controls. TSH concentration was lower in patients compared to controls (0.11±0.24 vs 2.15±1.12 MCR/IU per ml, respectively, P<0.01), and FT4 values higher (1.87±0.39 vs 1.17±0.15 ng/dl, respectively, P<0.01).

No significant differences were found between patients and controls in serum calcium, alkaline phosphatase, PTH, Vitamin D and testosterone, 24 h urinary calcium excretion and urinary N-telopeptides. There was no difference in BMD (Table) and neither patient nor control had a history of bone fracture.

Conclusions: Long-term suppressive levothyroxine treatment for DCT was not associated with decreased BMD or increased risk of fracture in men.