Thyroidal Effect of Metformin Treatment in Patients With Polycystic Ovary Syndrome

Mario Rotondi; Carlo Cappelli; Flavia Magri; Roberta Botta; Rosa Dionisio; Carmelo Iacobello; Pasquale De Cata; Rossella E. Nappi; Maurizio Castellano; Luca Chiovato

Disclosures

Clin Endocrinol. 2011;75(3):378–381 

In This Article

Results

When patients with PCOS were evaluated as a whole group, no significant change in the serum concentrations of FT4 and TSH was observed by comparing data found before and after the 4-month course of metformin treatment. However, when hormone data from euthyroid and hypothyroid (either treated or untreated with l-thyroxine) patients with PCOS were evaluated separately, a different picture emerged. In the twenty-four euthyroid patients with PCOS, the median serum levels of TSH before starting metformin were 1·4 mIU/l (range = 0·4–3·8 mIU/l) and did not significantly change after a 4-month course of metformin: 1·6 mIU/l (range = 0·4–3·7 mIU/l). Similarly, the median serum levels of FT4 did not significantly change being 15·9 pmol/l (range = 12·6–19·3 pmol/l) before starting metformin and 16 pmol/l (range = 14–19·3 pmol/l) after a 4-month course of the drug. In the nine hypothyroid patients with PCOS, either treated with l-thyroxine or untreated, the median pretreatment serum levels of TSH (3·2 mIU/l, range = 0·4–7·1 mIU/l) significantly decreased after a 4-month course of metformin (1·7 mIU/l, range = 0·5–5·2 mIU/l) (P < 0·05). The individual plots of serum TSH concentrations in the nine hypothyroid patients before and after metformin treatment are shown in Fig. 1. In these patients, no significant change in the median serum levels of FT4 before (15·9 pmol/l, range = 11·6–18·0 pmol/l) and after (15·9 pmol/l, range = 11·3–17·9 pmol/l) the 4-month course of metformin treatment was observed. None of our patient with PCOS and hypothyroidism experienced a suppressed TSH during metformin treatment.

Figure 1.

Individual plots of serum TSH concentrations before and 4 months after starting metformin treatment in hypothyroid patients with polycystic ovary syndrome.

Clinical and anthropometric findings did not significantly differ when comparing the 24 euthyroid PCOS patients with the nine hypothyroid ones. In particular, no significant difference emerged regarding median age and in BMI. More interestingly, no significant difference as to the mean administered dose of metformin was found between the 24 euthyroid and the nine hypothyroid patients with PCOS (1322 ± 402 mg vs 1406 ± 589, respectively). During metformin treatment, no significant change in the mean BMI score was observed, both in the 24 euthyroid patients (pretreatment = 31·0 ± 4·2 Kg/m2; posttreatment = 30·1 ± 3·7 Kg/m2) and in the nine hypothyroid (pretreatment = 29·9 ± 4·6 Kg/m2, posttreatment = 29·5 ± 4·4 Kg/m2) patients with PCOS.

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