Endocrine Abstracts

Subclinical hypothyroidism (SCH) is a common disorder and indications of treatment are still being debated. The aim of our study was to describe the therapeutic and evolutionary characteristics of SCH.

Methods: We undertook a longitudinal retrospective study in 110 patients with SCH biologically defined by increased serum thyroid-stimulating hormone (TSH) levels (>4 mIU/l) and normal FT4. Pregnancy, age less than 18 years, personal history of partial thyroidectomy or radioactive iodine therapy were exclusion criteria.

Results: Sixty-one (55.5%) patients were put under L-thyroxine therapy. The TSH level of treated subjects was significantly higher than that of untreated subjects (8.1 mIU/l vs 5.9 mIU/l, P<0.001). Thyroid peroxidase antibodies were more frequently positive in treated subjects (93% vs 7%, P<0.001). The dose of L-thyroxine which allowed the normalization of the TSH level was on average 63.9 μg±39.4 μg/day. There was no significant difference between the results of the metabolic parameters (weight, blood pressure, fasting glucose, total cholesterol, triglycerides and HDL cholesterol) before and after normalization of TSH level. In untreated patients, spontaneous TSH normalization occurred in 27% of cases after an average time of 3.5±3.1 months.

Conclusion: L-thyroxine replacement in patients with SCH concerned almost half of our patients. Higher TSH level and positive thyroid peroxidase antibodies were more frequently associated with L-thyroxine requirement. Spontaneous TSH normalization was relatively frequent (one quarter of untreated patients); hence repeating measurement of FT4 and TSH is necessary before starting L-thyroxine therapy.