Growth hormone deficiency in adults--an indication for therapy?

Growth hormone for adults

Images

The effect of growth hormone administration in growth hormone deficient adults on bone, protein, carbohydrate and lipid homeostasis, as well as on body composition

OBJECTIVE

The effect on bone, protein, carbohydrate and lipid homeostasis as well as body composition of the administration of growth hormone to adult patients with growth hormone deficiency was studied.

DESIGN

Growth hormone was administered at a dose of 25 micrograms/kg/day with a maximum of 1.48 mg (4 IU) a day, for 6 months in eight adults. Studies were done before the start and at 1, 3 and 6 months during therapy, as well as 3 months after treatment had been stopped.

RESULTS

Subjective well-being as assessed by a short psychological tests showed an improvement in six and no change in two patients. Body composition, as assessed by body impedance assessment and D2O dilution, both showed an increase in lean body mass of 4 kg (5% of body weight), accompanied by a decrease in mean fat mass of 3 kg. Nitrogen turnover studies showed a transient increase in fed state nitrogen balance due to an increase in the rate of protein synthesis, which exceeded a smaller increase in the protein degradation rate. Growth hormone treatment did not affect the circulating levels of 25(OH)-vitD or PTH 1-84, while 1,25(OH)2-vitD had significantly increased after 6 months, as well as 3 months after treatment ended. Osteocalcin, procollagen I levels, as well as 24-hour urinary excretion of hydroxyproline and calcium rose during growth hormone administration but subsequently decreased rapidly after administration had been stopped, while the increase in alkaline phosphatase persisted. This increase in markers of both bone resorption and bone formation indicates an activation of bone remodelling, but this was not reflected by an increase in bone density. Glucose levels, measured before and during a normal breakfast, increased during growth hormone treatment, but serum insulin levels did not. Total cholesterol levels decreased by 0.5 mmol/l. Levels of T4 and free T4 as well as rT3 decreased, while T3 increased during growth hormone treatment.

CONCLUSION

Therapy with growth hormone for 6 months in a dose varying between 6 and 25 micrograms/kg/day increased lean body mass and decreased fat mass. The sense of general well-being improved in most patients. Furthermore, growth hormone treatment increased bone turnover without a measurable increase in bone density, caused some minor changes in lipid and carbohydrate metabolism, and increased the metabolism of thyroxine to T3.

Changes in skeletal muscle and body composition after discontinuation of growth hormone treatment in growth hormone deficient young adults

OBJECTIVES

The aim of this study was to determine whether there are any changes in skeletal muscle strength and size and body composition following growth hormone (GH) withdrawal in GH deficient young adults.

DESIGN

A longitudinal, 1-year, open, uncontrolled study of the changes in skeletal muscle and body composition following GH withdrawal was performed. Endocrine status was reassessed at the end of the study period during an insulin tolerance test. Some measurements were repeated after 2 years of treatment.

PATIENTS

Twelve (11 male, one female; age range 14-21) patients who had been diagnosed during childhood as growth hormone deficient took part in the study. Four of the 12 patients were found to have a normal GH response on retesting at the end of the study and their results were analysed as a separate group.

MEASUREMENTS

Quadriceps and forearm flexor maximum voluntary isometric strength, body fat content and serum IGF-1 were measured at 3-monthly intervals over 1 year. Every 6 months muscle size was measured from computerized tomography scans and fibre area from quadriceps needle biopsy samples.

RESULTS

For the growth hormone deficient group the 12 month quadriceps strength, size and fibre areas were 94.0% +/- 8.5 (mean +/- SD), 94.5% +/- 6.3 and 85.6% +/- 17.7 respectively of control (baseline) values. Forearm flexor strength and size were 101.4% +/- 7.9 and 92.0% +/- 9.2 of control. Body fat percentage had increased from 19.5% +/- 8.6 to 24.1% +/- 9.5. No change was seen in the non-growth hormone deficient group.

CONCLUSIONS

Although the changes measured were relatively small they suggest a role for GH in the maintenance of muscle integrity and body composition in the young adult with growth hormone deficiency.

Growth hormone treatment in adults with growth hormone deficiency: effect on muscle fibre size and proportions

The effect of a 6-month period of substitution therapy with recombinant human growth hormone (rhGH) on muscle fibre size and muscle fibre type proportions has been investigated in a group of 13 adults with growth hormone deficiency. All had a peak growth hormone (GH) response to insulin-induced hypoglycaemia of less than 7 mU/l. There was no statistically significant change in the lesser fibre diameter or fibre proportions of either type 1 or type 2 muscle fibres in the rhGH group, as compared with placebo.

Changes in skeletal muscle after discontinuation of growth hormone treatment in young adults with hypopituitarism

Skeletal muscle strength and size were measured for 1 year following discontinuation of human growth hormone (hGH) treatment in 11 patients with hypopituitarism. Quadriceps and forearm flexor maximum voluntary isometric strength and size were measured. At the end of the study, endocrine status was reassessed by an insulin tolerance test. Three of the 11 subjects were found to have normal hGH secretion and were not included in the analysis. At 12 months, quadriceps strength, size and fibre areas were 94.0 +/- 8.5%, 94.5 +/- 6.3% and 85.6 +/- 17.7% (mean +/- SD), respectively, of baseline values. Forearm flexor strength and size were 101.4 +/- 7.9% and 92 +/- 9.2% of control values. Although these changes are relatively small, they suggest a role for growth hormone in the maintenance of muscle in the adult.