Hypogonadism in Systemic Diseases

Serum testosterone is often lower than normal in patients with acute or chronic systemic diseases. The underlying mechanisms involved in the reduced testosterone secretion depend on the type of systemic disease; thus, many pathogenetic mechanisms might be involved. These mechanisms involve the hypothalamus and the pituitary (secondary hypogonadism), the testis (primary hypogonadism), or both. The resulting low-serum testosterone could be reversible or not depending on the pathogenetic mechanism. Furthermore, the relationships between hypogonadism and the systemic disease are complex since these two clinical conditions may interact with each other in a bidirectional interplay. How to interpret low-serum testosterone in systemic diseases is not easy and univocal. Biochemical hypogonadism should be differentiated into overt clinical hypogonadism and functional hypogonadism, and testosterone treatment should be offered taking into account the primary systemic disease and the possible beneficial or harmful effect on it, as well as the presence of signs and symptoms of hypogonadism. In this chapter the main systemic illnesses associated with hypogonadism will be discussed together with their underlying pathogenetic mechanisms, clinical significance, relevance, and clinical and practical implications.