Question

Changes in GnRH pulse frequency in females is controlled by circulating levels of
A) Estrogen and progesterone
B) Estrogen and inhibin
C) Progesterone only
D) Progesterone and inhibin

Answer 1

As component of a large prohormone which is split enzymatically and further modified inside the secretory granules, GnRH is produced. Due to the sudden cleavage of peptidases, GnRH has a brief half-life of roughly 2-5 min.

Complete answer:
First we should know about GnRH to answer this question. The hypothalamus comprises neurons of the gonadotropin-releasing hormone (GnRH) that release pulsatile GnRH into the blood system of the hypophyseal portal from which it is transferred to the anterior pituitary gland. GnRH attaches to its gonadotrope cell receptor, enhancing gonadotropin biosynthesis and secretion, follicle-stimulating hormone (FSH), and luteinizing hormone (LH).
Now, let us find the solution from the options-

The hypothalamus develops the gonadotropin-releasing hormone (GnRH).
It induces the development of luteinizing hormone (LH) and, to a lesser degree, follicle stimulating hormone (FSH) in the pituitary gland.
However, estrogen levels decline with reduction of follicular numbers with resultant lack of negative feedback and consequent rises in GnRH secretion.
Progesterone at the hypothalamus stage also lowers GnRH secretion.

Thus, the correct answer is option (A) Estrogen and progesterone.

Note: Gonadal steroids feedback on the hypothalamus and pituitary to reduce GnRH and gonadotropin production in most physiological settings. An exception is suggested to be related to positive feedback from rapidly increasing Estradiol levels at the period of the preovulatory LH surge in females.