The Influence of Age on the 24-Hour Integrated Concentration of Growth Hormone in Normal Individuals*

TLDR

The study examined how aging influences spontaneously secreted growth hormone by measuring the 24‑hour integrated concentration of GH in 173 non‑obese adults aged 7–65 years. The authors assessed 24‑hour integrated GH concentrations in these subjects to evaluate age‑related changes. IC‑GH declines markedly with age after the second decade, correlates strongly with age (r = 0.73), is higher in children and during Tanner stage 5, but shows no sex difference, indicating that age and pubertal status must be considered when interpreting GH secretion.

Abstract

We examined changes in spontaneously secreted growth hormone with aging by studying the 24-h integrated concentration of GH (IC-GH) of 173 nonobese subjects (height, ≥5%; 7–65 yr of age). There was no significant difference in IC-GH on repeat testing of 13 men or in 23 women studied in the follicular and again in the luteal phase of the menstrual cycle. The level of IC-GH was strongly effected by age; children had the highest mean IC-GH, and there was a decline in IC-GH with increasing age after the second decade of life. The correlation of IC-GH with age was highly significant (r = 0.73; P < 0.0001). There was no difference in IC-GH between males and females when matched for age. The mean IC-GH at Tanner stage 5 of puberty (7.4 ± 2.0 ng/ml) was higher than that at stages 2–4 (5.7 ± 1.4; P < 0.0005) or that irl prepubertal children (5.8 ± 1.4; P < 0.001). Thus, age and pubertal status must be carefully considered when interpreting the IC-GH for patients suspected of having deficient or excessive secretion of GH.