Before the placenta functions the corpus luteum is the primary source of synthesis of which of the following… - NCL (MP) Nursing Officer - 2020

NCL (MP) Nursing Officer - 2020

Obstetrics & Gynaecology

Easy

Appeared in: NCL (MP) Nursing Officer - 2020

Explanation

In early pregnancy, before the placenta is fully functional, the corpus luteum is the main producer of key hormones required to sustain the pregnancy.
The corpus luteum is maintained by human chorionic gonadotropin (hCG), a hormone produced by the developing embryo after implantation.
The primary hormones synthesized by the hCG-stimulated corpus luteum are progesterone and estrogen.
Progesterone is essential for maintaining the uterine lining (endometrium) for the pregnancy, while estrogen supports uterine growth and blood flow.
This hormonal support continues until the 'luteal-placental shift' occurs at approximately 8-10 weeks of gestation, when the placenta takes over as the primary source of these hormones.

Option A: Thyroxine (T4) is produced by the thyroid gland, and Thyroid-Stimulating Hormone (TSH) is produced by the anterior pituitary gland. They are involved in regulating metabolism but are not synthesized by the corpus luteum.
Option C: Cortisol is a steroid hormone produced by the adrenal cortex, and thyroxine is a hormone produced by the thyroid gland. Neither is synthesized by the corpus luteum.
Option D: Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH) are gonadotropins produced by the anterior pituitary gland. They regulate the ovarian cycle, but their levels are suppressed during pregnancy. The corpus luteum is the target of LH (and later hCG), but it does not produce them.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Hormonal function of the corpus luteum in early pregnancy as background academic context rather than a clinical decision trigger.
Understanding the luteal-placental shift is critical for managing early pregnancy complications and providing patient education.
If a patient requires surgical removal of an ovary or a corpus luteum cyst (oophorectomy or cystectomy) before 10 weeks of gestation, she will need exogenous progesterone supplementation to prevent miscarriage, as the primary source of this pregnancy-sustaining hormone has been removed.
Low progesterone levels in early pregnancy can be a sign of a failing corpus luteum or a non-viable pregnancy, prompting closer monitoring.

How to Approach the Question

First, identify the key terms in the question: 'Before placenta functions,' 'corpus luteum,' and 'primary source of... hormones.' This directs your focus to the endocrinology of the first trimester.
Recall the sequence of events in early pregnancy: After ovulation, the follicle becomes the corpus luteum. If fertilization and implantation occur, the embryo produces hCG.
Remember the primary role of hCG: It 'rescues' the corpus luteum, stimulating it to continue its hormonal function.
Recall the main hormones produced by the corpus luteum: progesterone and estrogen.
Systematically evaluate the options. Eliminate hormones that are known to be produced by other glands (e.g., TSH from the pituitary, thyroxine from the thyroid, cortisol from the adrenal gland).
Confirm that the remaining option correctly identifies the hormones produced by the corpus luteum in early pregnancy.

Concept Tested & Keywords

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E6 Medicine Harrison 22e Part 2 p. 1032-1034

E6 Obstetrics Williams p. 71-95