Question

Which one of the following hormones is not involved in the process of parturition?

• A. Estrogens
• B. Cortisol
• C. Oxytocin
• D. Prolactin

Hint:

Hormones in Parturition vs Lactation:
$\bullet$ Parturition: Oxytocin (strong uterine contractions), Estrogen, Fetal Cortisol, Relaxin.
$\bullet$ Lactation (Milk production): Prolactin.
$\bullet$ Milk ejection letdown: Oxytocin.

Answer 1

The Correct Option is D

Concept:
Parturition (the process of delivering the baby) is induced by a complex neuroendocrine mechanism initiated by signals originating from the fully developed fetus and the placenta.

Step 1: Endocrine Mechanism of Parturition:
- The fully developed fetus and placenta induce mild uterine contractions called the fetal ejection reflex.
- Fetal adrenal glands release cortisol, which stimulates placental production of estrogens.
- An increased estrogen-to-progesterone ratio enhances uterine sensitivity to contractile stimuli and stimulates oxytocin receptor expression on myometrial cells.
- The fetal ejection reflex triggers the maternal posterior pituitary gland to secrete oxytocin.
- Oxytocin acts on the myometrium, causing strong, rhythmic uterine contractions, driving the expulsion of the baby.

Step 2: Role of Prolactin:
- Prolactin is synthesized and secreted by the anterior pituitary gland. Its physiological function is the synthesis and production of milk within the mammary alveoli during pregnancy and lactation.
- It is not involved in the physical process or hormonal cascade of uterine contractions during parturition.

Step 3: Final Answer:
Thus, Prolactin is not involved in the process of parturition (Option D).