Differential Diagnosis for Elevated Testosterone with Normal LH, FSH, and Prolactin

Single Most Likely Diagnosis

• Exogenous Testosterone Use: This is the most likely diagnosis because elevated testosterone levels with normal LH, FSH, and prolactin levels can indicate the use of exogenous testosterone, which suppresses the body's natural production of testosterone, leading to a feedback inhibition on the hypothalamic-pituitary-gonadal axis. However, in this case, LH and FSH are stated to be normal, which might suggest a different scenario or the early stages of use before significant feedback inhibition occurs.

Other Likely Diagnoses

• Testosterone-Secreting Tumors: Although less common, tumors of the testes or adrenal glands can produce testosterone, leading to elevated levels. Normal LH and FSH levels might be seen if the tumor's effect on testosterone production is not significantly altering the feedback inhibition on the pituitary gland.
• Congenital Adrenal Hyperplasia (CAH): Certain forms of CAH can lead to an overproduction of androgens, including testosterone. However, this condition typically presents with other abnormalities in hormone levels and is often diagnosed in infancy or childhood.
• Idiopathic Hyperandrogenism: This condition involves elevated androgen levels without a clear cause, such as polycystic ovary syndrome (PCOS) in women. However, PCOS typically presents with irregular menstrual cycles and other symptoms, and LH levels are often elevated.

Do Not Miss Diagnoses

• Adrenal Carcinoma: Although rare, adrenal carcinomas can produce androgens, including testosterone. Missing this diagnosis could be catastrophic due to the aggressive nature of these tumors.
• Leydig Cell Tumors: These are rare testicular tumors that can produce testosterone. Early detection is crucial for effective treatment.

Rare Diagnoses

• Familial Glucocorticoid Resistance: A rare condition where the body has a reduced response to glucocorticoids, leading to an overproduction of androgens due to ACTH stimulation of the adrenal glands.
• 11-Beta Hydroxylase Deficiency: A rare form of CAH that can lead to an overproduction of androgens, including testosterone. This condition is characterized by hypertension due to the accumulation of deoxycorticosterone (DOC), a potent mineralocorticoid.
• Gonadal Stromal Tumors: Rare tumors of the gonads that can produce sex hormones, including testosterone.

Each of these diagnoses requires careful consideration of the clinical presentation, laboratory findings, and potentially additional diagnostic testing to determine the underlying cause of the elevated testosterone levels.