Secondary Hypogonadism: Clinical Features and Endocrine Evaluation

Secondary hypogonadism, also known as hypogonadotropic hypogonadism, results from insufficient stimulation of the testes due to impaired hypothalamic or pituitary function. Unlike primary hypogonadism, where the testes fail directly, secondary forms originate from inadequate secretion of gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), or follicle-stimulating hormone (FSH).

Common causes include pituitary adenomas, systemic illness, obesity, chronic opioid use, hyperprolactinemia, and congenital disorders such as Kallmann syndrome. Clinical manifestations may include reduced libido, erectile dysfunction, infertility, decreased muscle mass, and fatigue.

Diagnostic evaluation involves measurement of morning serum testosterone levels alongside LH and FSH. Low testosterone with inappropriately normal or low gonadotropins suggests secondary hypogonadism. Magnetic resonance imaging of the pituitary gland may be required.

Management depends on reproductive goals. Testosterone replacement therapy may alleviate symptoms in men not seeking fertility, whereas gonadotropin therapy or pulsatile GnRH administration may stimulate spermatogenesis in men erotic desiring children.