In the event of a successful conception, which hormone is primarily responsible for 'rescuing' the corpus luteum to maintain progesterone production?

Appeared in: NORCET 5 Prelims - Sept 2023 (Shift-2)

Explanation

Following successful implantation, the syncytiotrophoblast cells of the developing embryo produce Human Chorionic Gonadotropin (hCG).
hCG is structurally similar to Luteinizing Hormone (LH) and acts on LH receptors in the corpus luteum.
This stimulation 'rescues' the corpus luteum from degenerating, ensuring it continues to secrete progesterone.
Sustained progesterone is essential for maintaining the endometrium (uterine lining) and supporting the pregnancy until the placenta takes over this function.

Option A: Luteinizing Hormone (LH) from the pituitary gland is responsible for forming and maintaining the corpus luteum during the luteal phase of a non-pregnant cycle. However, its levels naturally decline, and it cannot sustain the corpus luteum if pregnancy occurs.
Option C: Progesterone is the hormone produced by the corpus luteum; it does not rescue the corpus luteum itself. Its function is to prepare and maintain the uterine lining for pregnancy.
Option D: Follicle-Stimulating Hormone (FSH) is primarily involved in the first half of the menstrual cycle (the follicular phase), where it stimulates the growth and maturation of ovarian follicles.

Visual 1: Diagram - A graph showing the hormonal levels of LH, FSH, estrogen, progesterone, and hCG from ovulation through the first trimester of pregnancy. This would visually demonstrate the decline of LH and the sharp rise of hCG that coincides with the sustained high level of progesterone.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Hormonal regulation of early pregnancy and maintenance of the corpus luteum as background academic context rather than a clinical decision trigger.
The presence of hCG in blood or urine is the biological marker used in all standard pregnancy tests. A positive test confirms that implantation has occurred.
Monitoring hCG levels is a critical nursing role in early pregnancy. A slow rise or a fall in hCG levels can indicate an ectopic pregnancy or a non-viable pregnancy (miscarriage), requiring prompt medical intervention.
What if? - If a patient has an ectopic pregnancy (implantation outside the uterus), hCG will still be produced, but the levels often rise more slowly than in a normal uterine pregnancy. This abnormal pattern is a key diagnostic clue for this life-threatening condition.

How to Approach the Question

First, identify the core concept of the question: what keeps the progesterone-producing structure (corpus luteum) alive after conception?
Recall the normal menstrual cycle: LH from the pituitary maintains the corpus luteum, but only for about 14 days.
Consider the change introduced by the question: 'successful conception'. This means a new signal must be present to override the normal cycle.
Evaluate the options. The new signal must come from the embryo itself. Human Chorionic Gonadotropin (hCG) is known as the 'pregnancy hormone' produced by the embryo.
Connect the function: hCG mimics LH, binding to its receptors on the corpus luteum, thus 'rescuing' it and ensuring progesterone production continues. This makes hCG the correct answer.

Concept Tested & Keywords

Concept Tested: Hormonal regulation of early pregnancy and maintenance of the corpus luteum.
Stem keywords: conception, hormone, corpus luteum, progesterone production
Lead-in keywords: primarily responsible

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Practise the full NORCET 5 Prelims - Sept 2023 (Shift-2)

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