Does growth hormone (GH) naturally decrease with age?

Does Growth Hormone Naturally Decrease with Age?

Yes, growth hormone (GH) secretion naturally and progressively declines with age, beginning after puberty and continuing throughout adulthood, with 24-hour GH secretion rates in 60-year-olds often indistinguishable from those of patients with pathological pituitary disease. 1

Age-Related Pattern of GH Decline

Peak and Initial Decline

• GH secretion reaches its maximum around puberty, when production rates double to support the pubertal growth spurt 2
• By age 21, GH secretion has already begun to decrease and continues progressively thereafter 1
• The decline is characterized by markedly reduced pulse amplitude, though the pattern of pulsatile secretion remains similar to younger individuals 1

Progressive Adult Decline ("Somatopause")

• By age 60, most adults have total 24-hour GH secretion rates that are indistinguishable from those of hypopituitary patients with organic pituitary lesions 1
• This age-related decline in GH/IGF-I axis activity is termed the "somatopause" and results primarily from age-related changes in hypothalamic control of pituitary function 3
• IGF-I levels decline progressively with age, reflecting the impaired GH secretion 4

Clinical Significance of Age-Related GH Decline

Body Composition Changes

• The fall in GH secretion coincides with changes in body composition similar to those seen in adults with pathological GH deficiency 1
• These changes include:
  • Decrease in lean body mass 5, 4
  • Increase in body fat, especially visceral/abdominal fat 5, 3
  • The increase in central obesity can further inhibit GH secretion, creating a negative feedback loop 5

Metabolic and Functional Changes

• Adverse changes in lipoproteins occur with declining GH 5
• Reduction in aerobic capacity is observed 5, 3
• Changes in bone mineral density, cardiovascular function, immune system, and sense of well-being may occur 4

Important Distinctions

Normal Aging vs. Pathological GH Deficiency

• The endocrine pattern of normal aging is distinct from the decrease in GH/IGF-I levels associated with hypopituitarism 4
• In evaluating patients with clinical features suggesting GH deficiency, it is essential to assess for true GH deficiency through appropriate context (pituitary disease, childhood GHD) and GH stimulation testing before considering replacement 5

Remaining GH Responsiveness

• Sleep and exercise remain major stimuli for GH secretion even in older adults 1
• In elderly subjects, remaining GH secretion correlates closely with body composition, particularly lean body mass and inversely with central abdominal fat 1
• Physical exercise and increased fitness can increase GH production in adults, though the GH response to exercise is reduced with age 3

Clinical Caveat

While the age-related decline in GH is well-established, there is currently insufficient evidence to support routine GH replacement in normal aging outside of clinical studies, as long-term benefits, side effects, and risks remain inadequately characterized 5, 4. Elderly adults are much more susceptible to dose-related side effects including peripheral edema, carpal tunnel syndrome, and decreased insulin sensitivity 5.