Thyroid Dysfunction and Infertility

Thyroid hormones are required for regulating the metabolism and reproductive health. In females, ovarian cycle is regulated by synchronized action of thyroid hormones, luteinizing hormone (LH), follicle-stimulating hormone (FSH), and prolactin on hypothalamic-pituitary-ovarian axis.[1] The progesterone release from the corpus luteum occurs only when thyroid hormones act along with FSH, LH and hCG. Thyroid hormone receptors (TR-∂ 1 and TR ß1) are seen on ovarian surface epithelium and in oocytes of primordial, primary, and secondary follicles. They participate in complex regulation of ovarian function. In animal models, thyroid hormones synergize with FSH to exert direct stimulatory effects on granulosa cell function, such as morphological differentiation, LH/hCG receptor formation, induction of 3 ß -hydroxysteroid dehydrogenase, and aromatase.[2] They influence fertility by altering the GnRH and prolactin secretion, SHBG levels, and coagulation factors.