Question

Describe the hormonal changes that occur during the Ovarian and Endometrial Cycle

Answer 1

Estrogen is the main hormone which is concerned with both ovarian and endometrial cycle. Oestrogen has two peaks in which the first week is major and occurs about 48 hours before ovulation which by positive feedback causes LH surge responsible for ovulation. The second peak is minor and occurs in post mid luteal phase.

Along with the growth of ovarian follicle in the ovarian cycle oestrogen concentration slowly increases in the early part of follicular phase which is released from growing follicles.

After the ovulation later in mid secretory phase of endometrial cycle oestrogen concentration again in rises to some extent due to its release from corpus luteum.

Progesterone concentration is negligible in proliferative phase of endometrial cycle but later ovulation the concentration of progesterone reaches peak in 4 to 5 days.

The peak is due to increased secretion of progesterone from corpus luteum which is formed after ovulation. But the concentration decreases towards the end of luteal phase due to regression of Corpus luteum.

The luteinizing hormone levels remained low throughout the cycle except the day before ovulation during which the secretion of LH increasing sharply to reach a peak about 8 to 10 hours before ovulation called as LH surge.

The LH surge is due to positive feedback exerted by increased oestrogen levels and this is searches declines within 24 to 48 hours of ovulation. FSH levels increases to some extent in the early part of follicular phase for the development of follicles which coincides with the menstrual phase of endometrial cycle.

Then the FSH levels decline slowly but during ovulation, the FSH levels rise synchronously with the rise in LH levels and later it declines in secretory phase.