Follicle stimulating hormone, also known as FSH, is a naturally occurring hormone manufactured by the pituitary gland, essential to fertility for both women and men. In women, FSH regulates the menstrual cycle and is partially responsible for egg production; for men, FSH controls sperm production. FSH levels fluctuate naturally in healthy females according to their monthly cycle while FSH in healthy males stays at a constant level. When FSH levels are unusually high or low, it can signify health problems or fertility issues for both sexes. There are several reasons for rapid changes in FSH levels, for both healthy and unhealthy individuals.
A woman's FSH level rapidly rises immediately before ovulation. This is a normal and desirable change in FSH; it ensures proper production and release of the egg from the ovary. According to NaturalFertilityInfo.com, normal FSH levels for menstruating women during the follicular phase (before ovulation) and the luteal phase (after ovulation) should range from 5 to 20 international units per litre, or IU/L. During the mid-cycle peak immediately before ovulation, FSH levels should spike to between 30 and 50 IU/L.
Another normal change in a woman's FSH level occurs at menopause. When the ovaries stop producing oestrogen in menopause, FSH levels will rise and fall unpredictably, sometimes at a rapid rate. After menopause, however, FSH will usually regulate itself and stay at a constant level of 50 IU/L or higher.
Ovarian or Testicular Failure
Premature failure of the ovaries in women or primary testicular failure in men can cause FSH to spike to high levels. This failure and the subsequent changes in FSH can be due to injury such as infection, trauma, radiation or chemotherapy. It can also be caused by adrenal, thyroid or autoimmune disease, or by tumours on the ovary or testicle. Polycystic ovarian syndrome also commonly affects the ovaries and can cause a rapid rise in FSH.
Pituitary Gland Malfunction
A malfunction of the pituitary gland can cause rapid changes in FSH. Damage or trauma to the pituitary caused by tumours or inflammation processes of the brain, for example, can quickly reduce the production of FSH. Low levels of FSH can significantly interfere with a woman's cycle and a man's ability to produce sperm; in some cases, it can lead to infertility in both sexes.
Poor lifestyle choices, such as being underweight, smoking and exposure to chronic stress, can rapidly change FSH levels and adversely affect fertility. Those that are more than 15 per cent under their ideal body weight have too little body fat; this can result in an abnormal decrease of oestrogen and FSH. Smoking can cause an elevation in FSH levels; chronic stress tends to lower FSH levels.