As part of your infertility work-up you may have bloodwork done, to check out your hormone levels. This should always be done in men who have abnormal findings on their semen specimen.
Common Tests
The common tests are testosterone, estradiol, luteinizing hormone (or LH), follicle stimulating hormone (or FSH), and prolactin.
LH, FSH, and prolactin are made in a portion of the brain called the pituitary. Those hormones then control functions elsewhere in the body. LH primarily causes the production of testosterone in the testicles. A low LH could cause a low testosterone level. FSH primarily causes the production of sperm in the testicles. A low FSH could cause a low sperm count. A high prolactin can sometimes indicate a small tumor in the pituitary that then causes low LH and FSH levels and creates infertility.
The Importance of Testosterone
Testosterone is vitally important for male fertility. Testosterone helps men maintain a normal activity level, sexual interest and function, and metabolism. Most importantly, testosterone levels in the testicles help in sperm production. Low testosterone levels can impair sperm production. It can also cause erectile dysfunction. Low testosterone can occur due to problems with LH production or a problem in the testicle with testosterone production. It can also occur in men who are using testosterone supplementation with patches, gels, creams, and injections.
What About Estrogen?
Estradiol, a form of estrogen, is important in the regulation of male libido, erectile function, and sperm production. When estrogen levels are high it acts kind of like the Kryptonite of testosterone. Most important to infertility is that high estradiol level in men can cause impaired sperm production. A common cause of this is excess body fat. Testosterone is converted to estrogen in fat cells, so if you have too many fat cells you can end up with low testosterone and high estradiol ratio. When this happens you may have decreased sperm production resulting in infertility.