The Effect of Metformin on Hypothalamic-Pituitary-Thyroid Axis Activity in Women with Interferon-Induced...

One of the most frequent adverse effects of interferon-α therapy is thyroiditis. Metformin was found to improve insulin sensitivity in hepatitis C patients, as well as to reduce elevated thyrotropin levels in patients with hypothyroidism. The aim of this study was to investigate the effect of metformin on hypothalamic-pituitary-thyroid axis activity in patients with interferon-induced thyroiditis.

The study included 2 matched groups of women with type 2 diabetes and untreated subclinical hypothyroidism: patients with interferon-induced thyroiditis (n=8) and patients with Hashimoto's thyroiditis (n=12). Fasting plasma glucose, the homeostatic model assessment 1 of insulin resistance ratio (HOMA1-IR), glycated hemoglobin, the estimated glomerular filtration rate, as well as serum levels of thyrotropin, thyroid hormones, prolactin and insulin-like growth factor-1 (IGF-1) were assessed at baseline and after 4 months of metformin treatment.

Apart from reducing plasma glucose, HOMA1-IR and glycated hemoglobin, metformin decreased serum levels of thyrotropin. Circulating levels of thyroid hormones, prolactin and IGF-1 remained at a similar level throughout the study. The effect of metformin on serum thyrotropin was stronger in patients with interferon-induced thyroiditis than in patients with Hashimoto's thyroiditis, as well as correlated with its impact on insulin sensitivity.

Our results indicate that metformin may be an effective agent in patients with interferon-induced hypothyroidism.