The basal body temperature rises after ovulation due to?

AIIMS Bhuvneshwar NO- 2018

Obstetrics & Gynaecology

Easy

Appeared in: AIIMS Bhuvneshwar NO- 2018

Explanation

Following ovulation, the remnant of the ovarian follicle develops into the corpus luteum.
The corpus luteum produces large amounts of progesterone, making it the dominant hormone of the luteal (post-ovulatory) phase.
Progesterone has a thermogenic effect, meaning it acts on the hypothalamus in the brain to slightly increase the body's core temperature.
This results in a sustained rise in basal body temperature (BBT) of 0.3°C to 0.6°C, which is a reliable sign that ovulation has occurred.

Option B: Inhibin's primary function is to provide negative feedback to the pituitary gland, specifically to inhibit the secretion of Follicle-Stimulating Hormone (FSH). It has no known thermogenic effect.
Option C: Oestrogen is the dominant hormone in the follicular (pre-ovulatory) phase. While it influences the entire cycle, it does not cause the sustained temperature rise seen after ovulation. A peak in oestrogen triggers the LH surge that leads to ovulation.
Option D: Relaxin is primarily associated with pregnancy. It is responsible for softening the cervix and relaxing pelvic ligaments to prepare for childbirth. It does not play a role in the cyclical changes of basal body temperature.

Visual 1: Graph - A chart showing the 28-day menstrual cycle. The x-axis represents days, and the y-axis has plots for hormone levels (FSH, LH, Estrogen, Progesterone) and a separate plot for Basal Body Temperature. The visual should clearly show the BBT remaining low during the follicular phase and then rising and staying elevated after the LH surge and ovulation, coinciding with the rise in progesterone.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Hormonal regulation of basal body temperature during the menstrual cycle as background academic context rather than a clinical decision trigger.
Nurses educate patients on fertility awareness methods, including Basal Body Temperature (BBT) charting. Understanding that the post-ovulatory temperature rise is due to progesterone is key to explaining the method's scientific basis.
A 'monophasic' BBT chart (one without a clear temperature shift) suggests an anovulatory cycle, which is a critical finding for patients struggling with infertility. This can guide further investigation and intervention.
What if? If a patient's BBT chart shows a sustained temperature elevation for more than 18 days after ovulation, it is a strong presumptive sign of pregnancy. This is because the corpus luteum continues to produce progesterone under the influence of hCG from the developing embryo.

How to Approach the Question

First, identify the core concept of the question: the cause of a physiological change (BBT rise) related to a specific event (ovulation).
Recall the two main phases of the menstrual cycle: the follicular phase (pre-ovulation) and the luteal phase (post-ovulation).
Associate the dominant hormone with each phase. Oestrogen is dominant in the follicular phase, and progesterone is dominant in the luteal phase.
The question asks about a change after ovulation, which places the event in the luteal phase.
Therefore, the cause must be related to the dominant hormone of the luteal phase, which is progesterone.
Evaluate the options based on this knowledge. Progesterone is known for its thermogenic effect, making it the correct answer. The other hormones have different primary functions.

Concept Tested & Keywords

Concept Tested: Hormonal regulation of basal body temperature during the menstrual cycle.
Stem keywords: basal body temperature, ovulation
Lead-in keywords: due to

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