Several congenital and acquired conditions, originating from the hypothalamus and pituitary, or in other organs/systems with secondary systemic dissemination, can alter GH secretion leading to transient or chronic somatotroph deficiency or excess. The evolution of radiological, histological, and molecular techniques has profoundly changed the classification as well as treatment indications and types. Management is often challenging because of the heterogeneous and insidious presentation, the multi-organ involvement, and the variable outcome, so that patients should be referred to Pituitary Centers of Excellence. This volume addresses still open issues related to the diagnosis and treatment of GH deficiency and excess, in particular challenging physiologic and pathologic circumstances, and presents the new frontiers of diagnosis - including the application of artificial intelligence - and therapy towards precision, patient-tailored approach, aimed at maximizing treatment effectiveness, tolerability and patient adherence, and consequently, the employment of socio-sanitary resources.