Does estrogen replacement therapy, such as the pill or patch, affect the FSH test? If so, in what way? If not, why not?

R.R.

Recent findings in large-scale research studies suggest that HRT may increase a woman's risk of breast cancer, heart disease and stroke. In addition, when estrogen is prescribed alone, it may increase the risk of ovarian cancer. Consult a physician before starting any medication regimen.

FSH hormone rises during menopause. In fact, testing blood levels of FSH is a standard method for determining whether a woman is entering menopause and for evaluating the quality of her eggs.

FSH is a hormone produced by the pituitary gland in the brain. In a menstruating woman, FSH production varies during the course of the month depending on signals from the ovaries. If the ovary is functioning properly -- meaning it is preparing and releasing an egg on schedule -- it sends the hormones estrogen and inhibin into the bloodstream. When the pituitary detects these, it understands the ovary is sending the message "I'm OK and doing my job." When estrogen levels fall as part of the normal cycle, this sets off a chain of hormonal signals that triggers the pituitary to send out FSH, which in turn tells the ovaries to prepare another egg and step up production of estrogen again.

After menopause, the ovary stops releasing eggs, and ovarian production of estrogen and inhibin drops. In response, the pituitary gland tries to coax the "slacker" ovary back into action by secreting more FSH. Unfortunately, after all those years, the ovaries are enjoying retirement and don't even answer the phone when FSH comes calling.

With estrogen replacement therapy (ERT), the estrogen you receive will partially placate the pituitary "pit-boss." Sensing the influx of estrogen, the pituitary will ease up on its FSH production, but it won't be completely fooled -- "OK, OK, but I don't see any inhibin!" So, when you are taking ERT, the FSH will drop, but it will not drop all the way back to the levels you had before menopause.