Which hormone is responsible for the rise in basal body temperature at the time of ovulation?

• A. Progesterone
• B. Estrogen
• C. LH
• D. FSH

Answer: (A)

The rise in basal body temperature is caused by progesterone. After ovulation, the follicle becomes the corpus luteum and begins secreting progesterone, which slightly raises the body's temperature set-point. This thermogenic effect shows up as a noticeable bump in basal body temperature during the luteal phase and remains elevated until either pregnancy occurs or the corpus luteum regresses.

Estrogen largely drives the follicle-fertilization environment before ovulation and does not create this sustained temperature rise. LH triggers ovulation itself but does not cause the post-ovulatory temperature increase. FSH promotes follicle growth earlier in the cycle, not the temperature shift.