Growth Hormone Deficiency in Adulthood and the Effects of Growth Hormone Replacement: A Review

"GH DEFICIENCY in the human adult most commonly results from pituitary or peripituitary tumors and their treatment (1). The majority of these tumors are benign, and in a large series, pituitary adenoma was the commonest cause of adult hypopituitarism (2). The incidence of adultonset (AO) GH deficiency is not known, but indirect estimates based on the incidence of pituitary tumors suggest an incidence of 10 people/million annually. In contrast, childhood- onset (CO)GHdeficiency is most commonly idiopathic and is not necessarily associated with other pituitary hormone deficiencies. The limited supplies of pituitary-derived GH restricted research into the use of GH in adults and limited knowledge of the role ofGHafter the cessation of linear growth. An early study, in which a 35-yr-old hypopituitary adult reported increased vigor, ambition, and well-being after GH replacement, suggested that GH may have biological actions in adulthood (3). More recent evidence suggests that adults with hypopituitarism have reduced life expectancy (2, 4), possibly related to GH deficiency (5). The availability of recombinant GH has led to intensive investigation of the effects ofGHin health and disease, and over the past decade, numerous studies have focused on the effects of GH replacement in the adult with GH deficiency. The first placebo-controlled trials ofGHreplacement in the GH-deficient adult were reported in 1989 (6, 7). These and subsequent investigations have led to the recognition of a specific clinical syndrome in adults with long standing GH deficiency. This syndrome is associated with characteristic symptoms, signs, and investigative findings. The main features are listed in Table 1. Many studies have assessed the effects of GH replacement on these symptoms and signs. The majority of these data has resulted from both formal randomized placebo-controlled trials and smaller open studies. Consistently, these studies have demonstrated that adults with GH deficiency are both physically and psychologically less healthy than their age-matched peers, and that GH replacement results in substantial and sustained benefits. This review details the important features resulting from GH deficiency and summarizes the information, available up to the beginning of 1997, relating to the effects of GH replacement."