NEETZoologyChemical Coordination and Integration
Oral contraceptive pills containing a combination of synthetic progestogen and estrogen are highly effective in preventing pregnancy. What is the primary hormonal mechanism by which these pills prevent the release of an ovum?
Options
- AThey exert continuous negative feedback on the pituitary, inhibiting gonadotropin secretion and preventing the
- BThey directly induce the destruction of the Graafian follicle in the ovary before it reaches maturity.
- CThey stimulate a premature LH surge from the anterior pituitary before the ovarian follicle is fully mature.
- DThey block estrogen receptors on the ovarian surface to inhibit follicular growth and development.
Correct answer
A. They exert continuous negative feedback on the pituitary, inhibiting gonadotropin secretion and preventing the
Step-by-step solution
Normal ovulation requires a mid-cycle LH surge, which is triggered by a peak in natural estrogen (positive feedback). When a female takes oral contraceptive pills, the continuous exogenous supply of estrogen and progestogen maintains a constant negative feedback on the hypothalamus and anterior pituitary. This negative feedback inhibits the release of gonadotropins (FSH and LH). Without the LH surge, the Graafian follicle does not rupture, and ovulation is successfully prevented. Answer: They exert continuous negat