Which one of the following statements explains self-priming of gonadotrophs?
Lower GnRH pulse frequencies favour FSH secretion and higher frequencies favour LH secretion.
The correct answer is that lower GnRH pulse frequencies favour FSH and higher frequencies favour LH. GnRH is released from the arcuate nucleus in pulses, and the gonadotroph decodes their frequency. Repeated pulses up-regulate GnRH receptors so each successive pulse gives a bigger response — the self-priming effect. Rapid pulses (every 60–90 minutes, late follicular phase) selectively drive the LH beta-subunit and produce the mid-cycle surge; slow pulses (every 3–4 hours, when progesterone slows the pulse generator) favour the FSH beta-subunit for follicular recruitment.
The reversed option (low frequency favouring LH) contradicts this and would make the pre-ovulatory LH surge impossible. “Low frequency favours both” is wrong because slow pulsing suppresses LH relative to FSH. “High frequency favours both” is disproved clinically: continuous or very high-frequency exposure, as with GnRH agonists like leuprolide, down-regulates receptors and causes hypogonadotrophic suppression.
Key point: Fast pulses equal LH, slow pulses equal FSH, continuous exposure equals down-regulation — the basis of medical castration with GnRH agonists in fibroids, endometriosis and precocious puberty.
Similar Questions
Consider the following statements with respect to endometrial cycle:
1. The basal zone is uninfluenced by any hormone.
2. Saw-toothed glandular epithelium is seen in secretory phase.
3. Stratum compactum contains mainly the glands and less stroma.
4. Pseudostratification is seen in proliferative phase of menstrual cycle.
Which of the statements given above are correct?
When does the secondary oocyte complete the second meiotic division?
The growth and differentiation of primordial follicles is under the control of which hormone?
Important Questions from Physiology of Menstruation & Fertilization
- Implantation of a fertilised ovum occurs on which day following fertilisation?
- Withdrawal bleeding following administration of progesterone in a case of secondary amenorrhea indicates all EXCEPT:
- Diagnostic criteria for PCOD are:
1. Oligo/amenorrohoea
2. Hyperandrogenism
3. Polycystic ovaries on ultrasound
Which of the above are correct? An 18 year old unmarried girl comes with complaints of heavy, prolonged bleeding during menses. Which among the following investigations is NOT usually advised?
- Which one of the following is true about Basal body temperature?
1. Biphasic pattern
2. Increase in the level of progesterone and norepinephrine
3. Temperature falls by $0.5^{\circ}C$ after ovulation
4. It can predict ovulation precisely
Select the correct answer using the code given below:
