What is primary vs secondary hypogonadism?
Primary hypogonadism originates in the testes and shows elevated LH and FSH; secondary hypogonadism originates in the pituitary or hypothalamus and shows low LH and FSH.
Hypogonadism is low testosterone, but its cause determines how providers approach treatment. The distinction between primary and secondary hinges on which gland has failed.
Primary hypogonadism means the testes themselves are not producing adequate testosterone. In response, the pituitary gland tries to compensate by releasing more luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Blood work shows elevated LH and FSH paired with low testosterone. Primary causes include testicular injury, genetic disorders, or age-related decline in testicular function.
Secondary hypogonadism means the pituitary gland or hypothalamus is not sending proper signals to the testes. Both testosterone and the signaling hormones LH and FSH are low. Secondary causes include obesity, sleep apnea, chronic illness, or medication side effects that suppress the pituitary axis.
This distinction matters because treatment pathways differ. Primary hypogonadism typically requires testosterone replacement therapy to restore levels directly. Secondary hypogonadism may respond to medications that stimulate the pituitary to send signals to the testes, or it may also require testosterone replacement depending on the underlying cause and severity.
Testing hormone levels and understanding which type a patient has allows hormone therapy providers to choose the most effective protocol and set realistic expectations for recovery.