[Thyroid regulation pathways and its effect on human luteal function]

There are interferences between function of the thyroid gland and the ovary. Thus, thyroid disorders may influence the ovarian cycle. Up to now interferences in three main areas are described: the secretion of GnRH, i.e. FSH and, above all, LH, the peripheral metabolism of steroids (androgens, estrogens, and SHBG), and metabolism of prolactin. By employing human luteal cells, we were able to demonstrate that there is also a direct impact of thyroid regulation on luteal function: TSH, but not TRH or T3 or T4, possesses a luteotropic activity and reaches one fifth of the biological activity of hCG. This kind or direct influence may play an important role in the pathophysiology in patients with hypothyroidism.