Unit 8 HPG Axis

Question 1

Which hormone initiates the hypothalamic-pituitary-gonadal (HPG) axis?
a) LH
b) FSH
c) Estrogen
d) GnRH

Answer 1

d) GnRH

Explanation: Gonadotropin-releasing hormone (GnRH) is released by the hypothalamus in pulses and stimulates the anterior pituitary to release LH and FSH.

Question 2

What is the primary function of luteinizing hormone (LH)?
a) Stimulates oocyte maturation only
b) Supports Sertoli cells
c) Stimulates Leydig and thecal cells to produce steroid hormones
d) Inhibits GnRH release

Answer 2

c) Stimulates Leydig and thecal cells to produce steroid hormones

Explanation: LH targets hormone-producing cells in both sexes—Leydig cells (testosterone) and thecal cells (androgens).

Question 3

What is the role of follicle-stimulating hormone (FSH)?
a) Stimulates steroidogenesis in Leydig cells
b) Promotes gamete maturation via Sertoli and granulosa cells
c) Inhibits estrogen release
d) Stimulates progesterone receptors

Answer 3

b) Promotes gamete maturation via Sertoli and granulosa cells

Explanation: FSH targets Sertoli cells in males and granulosa cells in females to support gamete development.

Question 4

Which hormone exhibits both positive and negative feedback on the HPG axis?
a) Estrogen
b) Testosterone
c) GnRH
d) Inhibin

Answer 4

a) Estrogen

Explanation: Estrogen provides negative feedback at low/moderate levels but triggers positive feedback leading to the LH surge during the late follicular phase.

Question 5

What is the function of inhibin in reproductive endocrinology?
a) Inhibits LH secretion
b) Stimulates testosterone release
c) Selectively inhibits FSH release
d) Enhances GnRH secretion

Answer 5

c) Selectively inhibits FSH release

Explanation: Inhibin is secreted by Sertoli and granulosa cells and specifically downregulates FSH, not LH.