How much, and by what mechanisms, does growth hormone replacement improve the quality of life in GH-deficient adults?

The majority of studies (but not all) have demonstrated that adults with hy popituitarism of both childhood and adult onset have a diminished quality o f life (QOL) in comparison with the normal population. Reductions in physic al and mental energy, dissatisfaction with body image and poor memory have been reported most consistently. A specific role for growth hormone (GPI) d eficiency, as opposed to multiple pituitary hormone deficiency, has been ob served for the memory deficit, which extends to both short- and long-term m emory. Comparisons with normal siblings have confirmed the reduced QOL, alt hough differences have been small. There is less consensus far a reduction in QOL when hypopituitary subjects are compared with patients with other ch ronic diseases, with studies supporting tin comparison with diabetics) and refuting tin comparison with patients following mastoid surgery) the reduct ion in QOL. GH replacement in adults has improved QOL, particularly in the domains of energy level and self-esteem: and memory has improved. The socia l impact of these changes may be considerable, with patients requiring fewe r days' sick leave. A major placebo effect is present, however, and neutral results as well as positive have been reported in placebo-controlled trial s. Where a positive effect has been observed, it has been more likely to oc cur in patients with a low QOL at the outset. It is otherwise impossible to predict at the outset those who will benefit from GH replacement. GH treat ment has effects on body composition, exercise capacity, muscle strength, t otal body water and intermediary metabolism which would be expected to impr ove QOL. Replacement therapy also has side-effects, and it is the variable balance of the positive and negative effects, coupled with the difficulties of measuring QOL, which have led to the disparate results in the literatur e. There is probably also a true interindividual variation, although the me chanisms of this are currently unknown.