Q. Does the hypophysis- ovaries endocrine axis work in the same way during pregnancy as in non-pregnant women? If pregnancy does not occur how does another menstrual cycle begin?

The functioning of the hypophysis is altered during pregnancy since progesterone and estrogen levels remain elevated during the gestational period the production of GnRH (gonadotropin-releasing hormone) from the hypothalamus is inhibited. The lack of GnRH thus inhibits the secretion of LH and FSH from the hypophysis and a new menstrual cycle does not begin.

If pregnancy does not occur the lowering of progesterone and estrogen levels stimulates the production of GnRH by the hypothalamus. This hormone then hastens the adenohypophyseal secretion of LH and FHS that in their turn stimulate the maturation of follicles and the beginning of a new menstrual cycle.