Hypokalemia alters sex hormone and gonadotropin levels: Evidence that FSH may be required for luteinization

Hypokalemia produced different effects on steroid sex hormone concentration s in plasma and ovary in the mouse. Estradiol levels were slightly increase d, whereas circulating progesterone was markedly decreased in all estrous p eriods. The preovulatory surge of gonadotropins and the secondary surge of follicle-stimulating hormone (FSH) at estrus were also decreased, but basal levels of both gonadotropins were unaffected. Supplementation with luteini zing hormone (LH), FSH, or gonadotrapin-releasing hormone (GnRH) at proestr us rapidly normalized plasma and ovarian progesterone levels at this stage of the estrous cycle. Plasma progesterone levels at diestrus were restored only by combined treatment, at the periovulatory stage, with LH and FSH or GnRH but not by LH or FSH alone. The results demonstrate a lack of steroido genic activity in the corpus luteum of the potassium-deficient mice and, fu rthermore, that FSK plays an important role in luteinization in the hypokal emic mice. We conclude that alteration of the transcellular potassium gradi ent may affect the regulation of the periovulatory surge of gonadotropins a nd progesterone secretion, probably by altering the release of GnRH from th e hypothalamus. In addition, the results suggest that FSH may play a certai n role as a luteotropic hormone in mice.