Two people come to the clinic one day. First you see Ana, a 17 year old teenage girl. Ana comes with her mother, who’s worried because Ana hasn’t had her first period yet.
Upon physical examination, you notice that Ana is quite short for her age. In addition, she has a wide neck, broad chest, and poorly developed breasts with widely spaced nipples. You decide to perform a blood test, which reveals low estrogen levels and high FSH and LH.
Next, comes María, a 25 year old female who’s concerned because she hasn’t had her period for nine months now.
She’s sexually active, so the first thing you do is ask for a pregnancy test, which comes up negative.
When asked about physical activities, she refers to going for a 2-hour run every single day, plus swimming and then tennis on weekdays.
Regarding her diet, she’s very strict when it comes to avoiding fatty foods. On physical examination, you realize that María is underweight, and a blood test reveals low levels of estrogen, LH, and FSH.
Okay, now both Ana and María have amenorrhea, which is generally defined as the absence of menstruation in females of reproductive age.
Now, for menstruation to happen, an individual must have a regular female reproductive anatomy and sexual development, which is normally under control of the hypothalamic-pituitary-gonadal axis.
First, the hypothalamus secretes gonadotropin-releasing hormone, or GnRH for short, which goes to the anterior pituitary to stimulate the release of gonadotropic hormones, which are luteinizing hormone or LH, and follicle-stimulating hormone or FSH.
LH and FSH then stimulate the gonads to produce sex hormones; in females, LH and FSH stimulate the ovaries to secrete estrogen and progesterone, which are responsible for the female primary sexual characteristics.
These are the changes necessary for reproduction, including menstruation, ovulation, and uterine development.