The effect of growth hormone substitution on cognitive performance in adult patients with hypopituitarism

Abstract

Objective: Adult hypopituitary patients with growth hormone deficiency, though on adequate adrenal, thyroid or sex hormone replacement therapy, complain of attention and memory disabilities. During the past years several studies have evidenced that growth hormone (GH) may exert distinctive effects on the central nervous system and induce beneficial effects on psychological capabilities. The aim of our study was to determine whether a long-term replacement therapy of recombinant human growth hormone (rhGH) affects cognitive performance in adults with GH deficiency.

Design: A double-blind, randomized placebo controlled trial over 6 months, followed by an open period of 6 months of rhGH treatment.

Measurements: The assessment of cognitive performance comprised attention, verbal memory and non-verbal intelligence and was examined at baseline (0), at 3, 6, 9, and 12 months. In addition, emotional well-being and energy were assessed using the Nottingham Health Profile self rating questionnaire.

Patients: Eighteen hypopituitary patients, mean age 41.6 (range 21-63) years with adult onset GH deficiency were evaluated. Patients were on adequate and stable adrenal, thyroid, gonadal and desmopressin replacement therapy where necessary, but not substituted for GH deficiency.

Results: After 3 and 6 months of rhGH treatment in the closed label phase a significant improvement of attentional performance was observed compared to baseline in the rhGH group but not in the placebo group. After 6 months scores of attention were significantly different between rhGH and placebo treatment for the digit cancellation test and marginally different for the trail-making test. In contrast, long-term verbal memory and non-verbal intelligence did not improve compared to baseline during therapy and short-term memory improved both in the GH and the placebo group after 3 and 6 months. This was considered as a placebo or practice effect. In the open-label phase a further improvement of attention was found in the GH group and subsequent treatment with rhGH for 3 and 6 months in the placebo group also significantly improved attentional performance supporting the results of the rhGH group in the first 6 months of the double-blind phase.

Conclusion: RhGH treatment appears to have a beneficial effect on attentional performance in adult hypopituitary patients with GH deficiency when treated for at least 3 months. Our study does not support a role for GH in influencing verbal memory or non-verbal intelligence.