Ageing and the endocrine system

Ageing is characterized by undesirable changes in body composition and a decline in many physiological functions, leading to reduced physical fitness and increased susceptibility to illness. With the projected growth of the elderly population worldwide, the ageing process is likely to give rise to increasing demands on health and welfare service budgets. The WHO projects that between the years 2000 and 2050, the world’s population of persons aged 60 and over will more than triple, from 600 million to 2 billion (1). The proportion of the EU population aged 65 years and over is predicted to rise from 17.1% in 2008 to 30.0% in 2060, and the proportion aged 80 and over to rise from 4.4% to 12.1% over the same period (2).

Ageing is a complex and poorly understood process. In recent years, there has been considerable interest in the role of the growth hormone/insulin-like growth factor 1 (GH/IGF-1) axis. Prior to 1985, supplies of GH were limited as it was obtainable only from human pituitary tissue, largely restricting its use to the treatment of childhood short stature. The development of recombinant GH has made available theoretically infinite supplies of GH, and allowed exploration of the role of GH in adult pathophysiology.

While GH is best recognized for its stimulation of longitudinal bone growth in childhood, recent evidence has demonstrated that GH continues to play a central role in adulthood in the regulation of fat and protein metabolism, body composition, and many physiological functions. The steady decline in GH secretion through adulthood, termed the ‘somatopause,’ raises the possibility of involvement of the GH/IGF-1 axis in the structural and functional changes that accompany advancing age.

This chapter explores the role of the somatopause and reviews the evidence for GH as a strategy for modifying age-related deterioration.