Question

Why does estrogen/estradiol decline mid-cycle (about day 14 of a typical human female cycle)?

Answer 1

Estrogen levels increases and decreases during the cycle of female reproductive system. At the start of the cycle the estrogen levels are low and increases in the 11-12th day of the cycle which triggers the Leutenizing hormone (LH). Triggering Leutenizing hormone in turn triggers ovulation. The estrogen levels reach low at this point (on day 14th) for the follicles to mature and ovulate.

Then again the estrogen levels increses and decreses at the end and begins the cycle again.

The menstrual cycle of female consist of 2 cycles

1. Follicular phase

2. Luteal phase

On an average these cycles consist of 28 days which basically involves fluctuating estrogen and progesterone levels.

Follicular phase happens between 1 to 14th day of the cycle where on the day 1 estrogen and progesterone will be lower and during 11-12th day estrogen level increses which triggers leutenizing hormone (LH) from the pituitary gland within the brain.

Later in the cycle estrogen levels decline for the follicules to mature resulting in ovulation. The rise in leutenizing hormone (LH) triggers ovulation where the follicle ruptures and egg is released. Ovulation happens on the 14th day of the cycle.

After ovulation, the new structure is called the corpus luteum.

Luteal phase happens between 14th to 28th day of the cycle during which the estrogen levels begin to decline and the Progesterone levels begin to increase resulting in a relatively constant phase. Continued drop in estrogen and progesterone levels result in the end of the luteal phase and the next cycle begins. If the corpus luteum is not rescued by pregnancy, it will demise