Question

What signals the corpus luteum to continue to produce progesterone when a fertilized egg is approaching the endometrium?

Gonadotropins released by the sperm cause the corpus luteum to continue to produce progesterone.
The motion of the cilia in the fallopian tube causes the release of hCG which keeps the corpus luteum producing progesterone.
The trophoblast cells produce estrogen which maintains the function of the corpus luteum.
The syncytiotrophoblast cells produce hCG which keeps the corpus luteum producing progesterone.

Answer 1

The hormone hCG, produced by the syncytiotrophoblast cells of the blastocyst, signals the corpus luteum to produce progesterone, maintaining the endometrium for implantation of the fertilized egg. The correct answer is option 4.

Step-by-step explanation:

The signal that causes the corpus luteum to continue to produce progesterone when a fertilized egg is approaching the endometrium is the hormone known as human chorionic gonadotropin (hCG). This hormone is produced by the syncytiotrophoblast cells of the blastocyst, which is the developing embryo. hCG is structurally similar to LH (luteinizing hormone) and serves to preserve the function of the corpus luteum, ensuring that it continues to secrete progesterone.


Progesterone is essential for maintaining the endometrium, allowing the blastocyst to implant and support a new pregnancy. Without fertilization, the corpus luteum will degrade, leading to a decrease in progesterone and the onset of menstruation.