The Hypothalamus in BBT Limitations

The hypothalamus is a small gland found at the base of the brain, which fundamentally operates as a thermostat for reproductive hormones.  It controls the levels of a number of hormones produced by providing responses to and stimulation of the pituitary gland.

How does the hypothalamus works?

The hypothalamus produces gonadotropin-releasing hormone (GnRH), which signals to increase or decrease hormone production throughout the first phase of a women’s ovulatory cycle.  In the feedback response, the pituitary increases FSH production that then causes follicle production in the ovaries. The production of estrogen is then accomplished as the follicle enlarges. As estrogen levels increase, the FSH levels eventually decrease.  Once the follicles are mature, the hypothalamus signals a spike in luteinizing hormone (LH), which leads to ovulation 36 hours later.  If something within this course is uneven or missing, and the process of ovulation does not occur, infertility will result.

Irregular ovulation can be due to numerous factors, but most frequently is secondary to the failure of the ovary to produce a follicle that ovulates.  Anovulation occurs when the ovaries cannot release eggs for fertilization. Although this is a natural consequence of aging associated with menopause, it may occur earlier in some women.

Some factors in irregular ovulation are:


  1. Hyperprolactinemia – abnormally elevated prolactin levels. This may be due to a small tumor on the pituitary and may require medications and/or surgery.
  2. Thyroid dysfunction – hyperthyroidism or hypothyroidism.  Thyroid levels can cause irregular ovulation. Medications can be used to treat thyroid dysfunction.
  3. Adrenal disorders.  Androgens are male hormones, such as testosterone, produced by the ovaries and adrenal gland.  High levels may lead to oligo-ovulation.
  4. Environmental factors like pollution, radiation, etc.
  5. Excessive exercise, obesity, and/or stress

Fertility treatments are available for such cases.  In these situations, it is assumed that the fallopian tubes are still open, unless the patient has had a tubal ligation surgery. A special test called a hysterosalpingogram can be done to make sure that the fallopian tubes are open. If the patient has had a tubal ligation, she would need to have a tubal reversal performed to open the tubes again. Any patient who will be undergoing a tubal ligation reversal would benefit from a hormonal evaluation prior to the tubal reversal surgery to ensure that once her tubes were reversed, she would not have infertility from a hormonal issue.

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