Human Reproduction

After ovulation the ruptured follicle forms the corpus luteum, which secretes large amounts of progesterone.
Progesterone is essential for the maintenance of the thickened, secretory endometrium of the uterus.
If fertilisation does not occur, the corpus luteum degenerates towards the end of the cycle.
The level of progesterone in the blood then falls sharply.
Without progesterone the endometrium cannot be maintained; it disintegrates and is shed along with blood, which is menstruation.
The fall of oestrogen also contributes, but the immediate cause is the withdrawal of progesterone.
So the hormone is progesterone.

The seminiferous tubules of the testis are lined by two types of cells: the male germ cells and the Sertoli cells, which provide nutrition to the developing germ cells.
The anterior pituitary secretes two gonadotropins, LH and FSH, under the influence of GnRH from the hypothalamus.
FSH (follicle stimulating hormone) acts on the Sertoli cells and stimulates them to secrete certain factors, such as androgen binding protein and inhibin, which help in the process of spermiogenesis.
LH (luteinising hormone) acts on the Leydig (interstitial) cells and stimulates the synthesis and secretion of androgens.
GH controls body growth and prolactin controls milk formation.
So Sertoli cells are regulated by FSH.