Menstrual Cycle. Basics.

In honor of my current OB/GYN rotation... I will talk about the menstrual cycle.

There are 3 distinctive phases: 
1. Menses
     The 1st day of bleeding from the endometrium built by the previous cycle (lasts avg of 3 days)
2. Proliferative phase
     Growth of new endometrium. Driven primarily by ESTROGEN (last avg 10 days)
3. Secretory phase
     Begins with ovulation. Driven primarily by PROGESTERONE. Mucous secretions are seen in gland lumens. Near the end of this phase - neutrophils and hemorrhage can be seen as an early sign of the next menses.

Dysfunctional Uterine Bleeding
1. Menorrhagia = heavy bleeding at menses
2. Metrorrhagia = heavy bleeding between menses
3. Menometrorrhagia = both

Common causes of Dysfunctional Uterine Bleeding
1. Anovulatory cycles 
     Happens when hormones are imbalanced. No ovulation. Endometrium stays in proliferative phase... it eventually grows too thick and outgrows its blood supply... it begins to slough off which leads to untimely bleeding. Causes to rule out: menopause, thyroid, pituitary, adrenal gland, estrogen-secreting tumor, obesity, and chronic dz.
2. Inadequate luteal phase
     Caused by insufficient production of PROGESTERONE. Pts complain of amenorrhea, excessive bleeding, and/or infertility.

http://www.humanbodydetectives.com/blog/2011/05/healthy-woman-series-menstrual-cycles/

Source: Hardcore: Pathology by Carter E. Wahl