Question

a) Present a scheme to illustrate the regulation of the hypothalamic-pituitary-gonadal axis.

b) List the factors that can influence this axis.

c) Discuss the role of the pineal gland in female reproduction.

Answer 1

a) Hypothalamic pituitary gonadal axis: ( HPG axis)

b) Factors regulating HPG axis:

I) GnRH is gonadotropin releasing hormone released in hypothalamus acts on pituitary to stimulate the secretion of gonadotropins, LH and FSH.  

II) LH and FSH action on males for steroidogenesis:

LH combines with LH receptors in leydig cells and stimulate testis to secrete testosterone. FSH combines with FSH receptor in Sertoli cells for sperm cell maturation. Testosterone secteted has negative feedback on GnRH neurons and anterior pituitary gonadotrophs.

III) LH and FSH on females for steroidogenesis:

In the ovary, LH acts on theca and granulosa cells to produce Estrogen and Progesterone which has negative feedback on GnRH and anterior pituitary gonadotrophs.

c) Role of pineal gland in female reproduction:

Pineal hormone, Melatonin inhibits the maturation of female reproductive organs during pubertal development.

Melatonin performs 2 functions in reproductive phase. i) By timing LH peak, it acts as a coordinating signal for menstrual cycle. ii) it supports progesterone production.

During menopause, age related endocrine changes occur due to gradual decline of age related circulating melatonin.

Role of pineal gland in breast cancer: Treatment with Melatonin or with pineal peptide preparation Epithalamus and Epitalon prevents breast cancer risk in women.