Responsible for kicking off a long chain of events that spurs sperm production, Follicle Stimulating Hormone (FSH) is the best hormonal indicator of the testicle’s ability to produce sperm and a primary hormone to be measured in the evaluation of male fertility.
What is Follicle Stimulating Hormone?
FSH is the hormone responsible for the maturation of eggs in women. If you’ve been researching fertility for a while, your wife may have had an FSH test to ensure that her eggs were “good.” You may have also leaned that synthesized FSH is often given as an injectable medication to regulate ovulation and the maturation of eggs. During IVF, it is used to hyper-stimulate ovaries to produce multiple eggs for retrieval.
FSH is equally important in men. It plays a critical role in sperm production. There is a complicated hormonal feedback system between the brain and the balls that enables the testicles to accomplish their two primary jobs of producing sperm and testosterone. The process starts in the brain where the hypothalamus (the part of your brain that regulates things like hunger, sleep and body temperature) releases a hormone called Gonadotropin-releasing Hormone (GnRH). GnRH flows down to the pituitary gland and stimulates the release of LH and FSH. FSH gets into the blood stream which takes it to the testicle. Once in the testicle, FSH stimulates germ cells to divide, which is the first step in spermatogenesis. FSH is also absorbed by testicular sertoli cells enabling them to “nurse” baby sperm and help them to develop properly. Normal sperm production requires a minimum level of FSH, LH and Testosterone.
To measure FSH levels, men need to get a blood test done. Typically, to fully evaluate male fertility, doctors will order a blood test to measure a panel of hormones which usually includes FSH and Testosterone. They may also add Luteinizing Hormone, Estrodial and Prolactin which will provide additional information and insight into your hormonal health.
In a normal day, hormone levels cycle from high to low. Testosterone naturally peaks first thing in the morning (partially responsible for morning wood) For this reason, doctors prefer to measure hormones between 8-10am to get a snap shot of your hormone profile when Testosterone level is likely to be highest.
When preparing for a FSH test there are a few things to make sure your doctor is aware of:
- Current medications
- Current or past use of testosterone supplements, anabolic steroids, clomid or other performance enhancers (If you are using something at the gym and aren’t quite sure what it is, you should bring it with you to the appointment.)
- Recent use of marijuana as it my decrease a number of hormones levels, including FSH
Normal FSH range for adult men: 2-7 mIU/mL
Reference ranges reported for FSH vary greatly from lab to lab. Some have ranges as large as 1-20mIU/mL. These reference ranges are not typically considering “normal” to be a “fertile” range, rather the ranges that can be observed in a large population of men. Normal FSH values for fertility are typically reported between 1-11.1mIU/mL, several recent studies suggest a tighter range of 2-7mIU/mL as more indicative of predicting normal sperm production in men.
Many studies have shown that FSH levels are closely linked to sperm production and can provide a good, non-invasive window into how well the testicles are working. A large study of over 2,000 men showed an average FSH value of 4.2 mIU/mL with a range of 1.8 – 6.8 for men with a normal semen analysis. Other studies comparing fertile and infertile men showed that fertile men typically had FSH levels from 2-5 mIU/mL. Men with low sperm counts often had FSH values that were slightly elevated, ranging from the 5-8.5 uIU/mL. FSH levels above 8 typically correlate with additional reductions in sperm count. Men with azoospermia will often have FSH values above 10 uIU/mL which can go as high as 40 or 50uIU/mL. Sometimes azoospermia can be caused by a blockage that prevents sperm from exiting the body rather than a failure by the testicle to produce sperm to begin with. In these cases, azoospermic men will often have normal FSH numbers and are good candidates for corrective surgeries or sperm extractions.
What causes high FSH in Men?
Typically, if FSH is high then some sort of damage is causing the testicle to not function as well and the pituitary gland is trying to compensate by going into overdrive and flooding the balls with extra FSH to support spermatogenesis. In cases like this, FSH levels are often off the charts high sometimes double or triple the normal values. Common causes for this include:
- Chromosome abnormalities such as Klinefelter’s syndrome or Y Chromosome Deletions
- Childhood problems such as maldecent of testicle or testicular torsion
- Injury that causes significant damage to testicular tissue
- Viral infection (most commonly mumps) that damages testicle
- Radiation exposure or chemotherapy
- Testicular cancer
What causes low FSH in Men?
The most common reason for FSH deficiency in men is the use of external androgens (testosterone, anabolic steroids or other performance enhancers). External androgens trick the brain into thinking the body is producing naturally high levels of testosterone which shuts down production of follicle stimulating hormone and consequently sperm production. This is most exaggerated in men who have used steroids for long periods of time.
The second most common cause of low FSH levels is a health issue that directly impacts the function of the pituitary gland itself. Most common causes of pituitary malfunction include:
- Genetic conditions such as Kallman’s Syndrome or Prader-Willi Syndrome
- Pituitary tumors (cancerous and benign)
- Head trauma
- Various Medications
- Auto-immune disorders
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