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Clin Endocrinol (Oxf). 2011 Sep;75(3):378-81. doi: 10.1111/j.1365-2265.2011.04042.x.

Thyroidal effect of metformin treatment in patients with polycystic ovary syndrome.

Author information

1
Unit of Internal Medicine and Endocrinology, Fondazione Salvatore Maugeri IRCCS, ISPESL Laboratory for Endocrine Disruptors, University of Pavia, Pavia, Italy.

Abstract

OBJECTIVE:

Metformin is widely used for the treatment of type 2 diabetes. Growing evidence supports the beneficial effects of metformin also in patients with polycystic ovary syndrome (PCOS). It was recently reported that metformin has a TSH-lowering effect in hypothyroid patients with diabetes being treated with metformin.

DESIGN:

Aim of this study was to evaluate the effect of metformin treatment on the thyroid hormone profile in patients with PCOS.

PATIENTS AND MEASUREMENTS:

Thirty-three patients with PCOS were specifically selected for being either treated with levothyroxine for a previous diagnosis of hypothyroidism (n = 7), untreated subclinically hypothyroid (n = 2) or euthyroid without levothyroxine treatment (n = 24) before the starting of metformin. The serum levels of TSH and FT(4) were measured before and after a 4-month period of metformin therapy.

RESULTS:

Thyroid function parameters did not change after starting metformin therapy in euthyroid patients with PCOS. In the 9 hypothyroid patients with PCOS, the basal median serum levels of TSH (3·2 mIU/l, range = 0·4-7·1 mIU/l) significantly (P < 0·05) decreased after a 4-month course of metformin treatment (1·7 mIU/l, range = 0·5-5·2 mIU/l). No significant change in the serum levels of FT4 was observed in these patients. The TSH-lowering effect of metformin was not related to the administered dose of the drug, which was similar in euthyroid as compared with hypothyroid patients with PCOS (1406 ± 589 vs 1322 ± 402 mg/day, respectively; NS).

CONCLUSIONS:

These results indicate that metformin treatment has a TSH-lowering effect in hypothyroid patients with PCOS, both treated with l-thyroxine and untreated.

[Indexed for MEDLINE]

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