Thyroid function during ovarian stimulation: a systematic review

Objective: To review the evidence regarding thyroid function and thyroid autoimmunity (TAI) changes in women undergoing ovarian stimulation (OS).

Design: Studies eligible for the systematic review were those that reported data on thyroid function or TAI both before and during OS or within 1 month after OS.

Setting: Academic hospital.

Patient(s): Women with abnormal thyroid function or TAI (n = 419) and controls (n = 425).

Intervention(s): Ovarian stimulation.

Main outcome measure(s): Serum TSH, free thyroxine, free tri-iodothyronine and thyroid antibodies.

Result(s): Seven studies, between 2000 and 2011, were included. Serum TSH concentrations were significantly increased in three studies and were not changed in two studies. Serum free thyroxine concentrations were increased in two studies, were not changed in one, and were decreased in another. Serum free tri-iodothyronine concentrations were not changed in the only study in which they were measured. Thyroid antibody concentrations were decreased in one study and were not changed in two studies, even in the presence of changes in thyroid function.

Conclusion(s): The current evidence is inconclusive regarding OS effect on thyroid function or TAI. Serum TSH concentrations may be increased during or within 1 month after OS, exceeding the threshold of 2.5 mU/L suggested for the first trimester of pregnancy, but further prospective studies are needed to provide conclusive evidence for or against universal evaluation of thyroid function and TAI in women undergoing OS.