Luteinizing hormone (LH) is found in both males and females, and it is needed for reproduction. Luteinizing hormone in males is essential for the release of testosterone, which is necessary for sperm production, so low levels of LH can lead to infertility. This hormone is released by the anterior pituitary gland, which also produces follicle-stimulating hormone (FSH), so most males who have abnormal levels of LH also suffer from inadequate amounts of FSH. A man's levels of LH and FSH can be tested if there is a concern regarding the amount of sperm being produced, leading to problems impregnating a woman. A low level might indicate the delayed onset of puberty, low body weight, or problems with the hypothalamus or pituitary gland.
After the onset of puberty in males, the hypothalamus produces gonadotropin-releasing hormone (GnRH), which then stimulates the pituitary to produce LH. This hormone then stimulates the interstitial cells in the testes to create testosterone, which is why luteinizing hormone is sometimes referred to as interstitial cell stimulating hormone (ICSH) in men. Testosterone is the main male sex hormone, and it is necessary in order for males to develop their secondary sexual traits and produce sperm. Low levels of LH in males can therefore cause infertility and the absence of the typical male characteristics, such as facial hair and a deeper voice after puberty.
Most males do not know about their low level of LH until they notice symptoms that point to low levels of testosterone. For example, if the voice fails to deepen, body hair does not appear, and the breast tissue enlarges during puberty, there might be a hormonal imbalance. Inability to conceive a child with a female sexual partner might also be a sign of inadequate hormone levels. The underlying issue usually needs to be diagnosed and treated for the man to become fertile or improve his secondary sex characteristics, so many medical professionals will offer testing.
In most cases, a blood test can measure the level of luteinizing hormone, and the results usually are available within one day. A high level of luteinizing hormone in males might indicate that the testicles are either not present or are damaged, though Klinefelter syndrome might also be the cause of this type of imbalance. On the other hand, insufficient levels might signal damage to the hypothalamus or pituitary gland. Low body weight, sometimes because of an eating disorder, also can result in low levels of this hormone, although late onset of puberty can have the same effect.