CAUSES OF INFERTILITY
Ovulation must occur regularly for successful pregnancy to result. During each month’s menstrual cycle, the female’s reproductive system undergoes changes to facilitate the development of the eggs within the ovarian follicles and the embryos implantation into the endometrium. The hormonal “system” that regulates ovulation is known as the “hypothalamic-adrenal-pituitary axis”. These hormonal events are initiated and monitored by the hypothalamus, a small gland at the base of the brain.
During the first days of the monthly cycle, the hypothalamus releases gonadotropin releasing hormone (GnRH) which travels to the pituitary signaling the production of follicle stimulating hormone (FSH). FSH is the hormone responsible for recruiting follicles and supporting their continued development. FSH (Gonal-F, Follistim, Repronex, Menopur, and Bravelle) is administered by injection in an IVF cycle to cause many follicles to develop.
As healthy follicles develop, they produce increasing amounts of estrogen which is monitored by the hypothalamus. Rising estrogen levels cause the hypothalamus to secrete GnRH to lower the production of FSH. Once the follicles mature, the hypothalamus signals the pituitary to release a surge of luteinizing hormone (LH) which initiates the final stages of follicular maturity and induces ovulation approximately 36 hours later.
After ovulation, the follicular structure remaining on the ovary is known as the corpus luteum. The corpus luteum begins progesterone production to cause the endometrium to develop and become more vascular to accept and support a developing embryo. Estrogen also supports endometrial development. If there is inadequate progesterone, a luteal phase defect could be present, meaning the endometrium does not develop properly.
Once the placenta forms, it begins to produce progesterone to support the pregnancy.
All of the above processes must occur properly or an ovulatory disorder could result, which is a common cause of infertility. Ovulatory disorders are usually treated with Clomid, letrozole, metformin, FSH, or Parlodel depending upon the cause.
Day three hormone testing of FSH, LH, TSH (thyroid) and other hormones is conducted to rule out many infertility disorders. For example, an elevated FSH level (>10 mIU/ml) may indicate reduced ovarian reserve or impending menopause. Abnormal thyroid hormone levels can also cause irregular ovulation and increased miscarriage rates.
Other hormone measurements may include inhibin, prolactin, and many more. Prolactin is known as the “breast milk hormone” because it stimulates milk production in pregnant females. Abnormally elevated prolactin levels (hyperprolactinemia) in women who are not pregnant can lead to irregular or no, ovulation. This condition is sometimes caused by a small tumor on the pituitary gland that can usually be treated medically or surgically.
Anything that affects reproductive hormone levels can lead to ovulatory disorders. PCOS is a good example where excessive androgen hormones are created leading to anovulation and other conditions.
Stress and excessive exercise can cause ovulatory disorders because of their effects on the production of reproductive hormones, particularly androgens. Smoking can also lead to ovulatory disorders.
Vaginal probe ultrasound allows the physician to visualize the follicles developing on the ovaries and ovulation can be documented.
Ovulation can be assessed by several methods including basal body temperature monitoring, luteinizing hormone (LH) urine test kits, progesterone measurements, and ultrasound evaluation. Most physicians no longer recommend BBT charting because it is inconvenient and much less accurate than other methods.
We recommend the LH urinary test kit, which measures the surge in luteinizing hormone that occurs prior to ovulation. Testing of the urine should begin around day 10 of the cycle and when ovulation is detected intercourse can be planned.