Differential Diagnosis for a 70-year-old man with low testosterone, high LH, and normal prolactin

• Single most likely diagnosis:
  • Primary hypogonadism: This condition is characterized by low testosterone levels and elevated luteinizing hormone (LH) levels, indicating that the testes are not producing enough testosterone, leading to an increase in LH secretion by the pituitary gland in an attempt to stimulate testosterone production. The normal prolactin level helps to rule out prolactinoma, which could also cause hypogonadism but typically presents with elevated prolactin levels.
• Other Likely diagnoses:
  • Testicular failure due to aging: As men age, the testes' ability to produce testosterone can decline, leading to primary hypogonadism. This condition is common in older men and can be associated with a variety of symptoms, including low libido, fatigue, and osteoporosis.
  • Testicular atrophy: This can result from various causes, including trauma, infection, or autoimmune disorders, leading to decreased testosterone production and elevated LH levels.
• Do Not Miss diagnoses:
  • Testicular cancer: Although less common, testicular cancer can cause testicular atrophy and lead to primary hypogonadism. It is crucial to examine the testes and consider imaging studies if a mass is suspected.
  • Hemochromatosis: This genetic disorder leads to iron overload, which can cause testicular damage and result in primary hypogonadism. Early diagnosis is critical to prevent long-term complications.
• Rare diagnoses:
  • Myotonic dystrophy: A genetic disorder that can affect the testes and lead to primary hypogonadism, among other systemic symptoms.
  • Klinefelter syndrome: A chromosomal disorder (47,XXY) that affects testicular development and function, leading to primary hypogonadism. Although typically diagnosed in younger men, some cases may not be identified until later in life.
  • Sertoli cell-only syndrome: A rare condition where the seminiferous tubules of the testes contain only Sertoli cells, leading to azoospermia and primary hypogonadism.