Thyroidal Effects of Metformin Treatment in Patients with PCOS

(click the title above to get to the paper)

Mario Rotondi et al.

Clin Endocrinol. 2011;75(3):378–381

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 FT4 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.

PTU dangerous?

June 3, 2009 — The US Food and Drug Administration (FDA) issued a safety alert today about the risk for serious liver damage, including liver failure, or death with propylthiouracil (PTU) compared with methimazole. Both agents are approved for the treatment of hyperthyroidism associated with Graves' disease.

“Health care professionals should carefully consider which drug to initiate in a patient recently diagnosed with Graves’ disease," Amy Egan, MD, deputy director for safety, Division of Metabolism and Endocrinology Products, in the FDA’s Center for Drug Evaluation and Research, said in a news release. "If PTU therapy is chosen, the patient should be closely monitored for symptoms and signs of liver injury, especially during the first six months after initiating therapy.”