Follicle stimulating hormone (FSH) levels fluctuate due to various health related factors. In women, menopause or ovarian failure will most likely cause an increase in luteinizing hormone (LH) and FSH levels. Primary testicular failure or developmental defects in men can cause an increase of FSH. Low levels of FSH can be attributed to pituitary or hypothalamic issues in both men and women.
Women with normally induced perimenopause or menopause are likely to have elevated levels of FSH; however, high amounts of FSH in younger women can signal an abnormal reproductive condition. Increased levels of FSH in non-menopausal women often indicate primary ovarian failure. Failure of the ovaries can be due to development defects, certain cancer treatments and chronic diseases.
Developmental defects that lead to an increase of FSH levels in women are ovarian agenesis, Turner’s syndrome and 17 alpha-hydroxylase deficiency. Ovarian agenesis is the developmental failure or absence of one or both ovaries. Turner’s syndrome is a chromosomal abnormality that can potentially cause ovarian agenesis. A condition called 17 alpha-hydroxylase deficiency causes a defect in the ovaries that results in abnormal production of steroid hormones.
Similar to women, men with developmental defects are likely to show high levels of FSH. Gonadal agenesis and chromosomal abnormalities are two types of developmental conditions that can be responsible for testicular failure and consequently elevated FSH levels. Gonadal agenesis is the absence or a failure to develop gonads. Klinefelter's syndrome is a chromosomal defect that is characterized by male hypogonadism; a high level of FSH is also indicative of primary hypogonadism.
Cancer treatments such as radiation and chemotherapy can interfere with reproductive functions in both men and women. Women may experience ovarian failure, while men will most likely experience testicular failure. For some, reproductive failure is reversible with the cessation of radiation and chemotherapy. Chronic conditions such as autoimmune disorders, adrenal disease and polycystic ovary syndrome (PCOS) can also contribute to high FSH levels.
In both sexes, a pituitary tumor can cause low levels of FSH and LH. In addition to low FSH and LH, men will also have low testosterone levels. Consequently, men with low testosterone will suffer from low sex drive and the inability to produce sperm. Women who have prolactin-producing tumors will cease to ovulate and menstruate.
Along with low FSH and LH levels, overall estrogen will drop. Pituitary tumors have different growth patterns and affect people in different ways. In some people FSH levels are high while in others the levels may only be slightly elevated.