Which of the following hormones causes ovulation?

Appeared in: IGNOU PB Bsc Entrance-2022

Explanation

The primary trigger for ovulation is a rapid and significant increase in Luteinizing Hormone (LH), known as the LH surge.
This surge typically occurs about 24-36 hours before ovulation, peaking approximately 16 hours prior to the event.
The high level of LH causes the mature ovarian follicle to rupture and release the ovum (egg).
Following ovulation, LH also stimulates the remaining follicular cells to transform into the corpus luteum, which produces progesterone.

Option A: Follicle-Stimulating Hormone (FSH) is responsible for the growth and development of ovarian follicles, but it does not directly trigger their rupture (ovulation).
Option C: Although both FSH and LH are essential for the complete menstrual cycle and follicular maturation, the final act of ovulation is triggered specifically by the LH surge alone.
Option D: Human Placental Lactogen (HPL) is a hormone of pregnancy, produced by the placenta. It is not involved in the regulation of the menstrual cycle or the process of ovulation.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Hormonal control of ovulation as background academic context rather than a clinical decision trigger.
Understanding the LH surge is the basis for ovulation predictor kits (OPKs) used for family planning. These kits detect the rise in urinary LH to predict the most fertile window.
In fertility treatments (e.g., IVF), a drug that mimics LH, Human Chorionic Gonadotropin (hCG), is often administered to trigger final follicular maturation and induce ovulation at a precise time.
What if? If a patient has a condition like Polycystic Ovary Syndrome (PCOS) with persistently high LH levels but no surge, they may experience anovulation (lack of ovulation), leading to irregular cycles and infertility.

How to Approach the Question

First, identify the key process in the question: 'causes ovulation'.
Recall the main hormones involved in the female menstrual cycle: FSH, LH, estrogen, and progesterone.
Differentiate the primary roles of each hormone. Associate FSH with 'follicle growth' and LH with 'ovulation trigger' and 'corpus luteum formation'.
Remember the term 'LH surge' as the specific event that directly precedes and causes ovulation.
Evaluate the options. Eliminate any hormones not involved in the menstrual cycle, such as HPL, which is related to pregnancy.
Select the hormone whose peak activity is the direct cause of ovulation.

Concept Tested & Keywords

Ql6_8_nvqe22NrhAzmYhK6

E6 Physiology Guyton 4SAE Part 3 p. 35-37

E6 Pharmacology Katzung 16e p. 1049-1051

Practise the full IGNOU PB Bsc Entrance-2022

Attempt every question from this paper in a timed mock, then review the full solution for each one.