Do your hormones influence how quickly you age?

Hormones are one factor that shapes how your body ages, but the relationship is nuanced. The menopause in women is a clear example: as oestrogen falls, fat shifts towards the abdomen. That abdominal fat in turn increases the risk of cardiovascular disease and type 2 diabetes. The menopause does not cause weight gain as such, but the distribution of fat does change in a demonstrable way.

Testosterone, growth hormone and IGF-1 (a growth-promoting hormone) also decline with age. This makes it harder for muscles to synthesise proteins, so muscle mass and muscle strength gradually decrease. This is called sarcopenia. In younger older adults, almost 9 percent are clinically meaningfully affected; in the oldest men that figure rises to almost 18 percent. Sarcopenia increases the risk of falls, bone loss and insulin resistance. In addition to the hormonal decline, low-grade inflammatory processes also play a role, although the precise contribution of each has not yet been fully established.

Growth hormone occupies a special position. In animals, high growth hormone levels lead to a shorter lifespan. In people with a congenital deficiency of or resistance to growth hormone, the risk of typical age-related diseases is indeed reduced, but the lifespan itself does not appear to be longer as a result. It therefore seems that growth hormone influences the number of years spent in good health more than it influences total lifespan. Furthermore, abdominal fat can suppress the production of growth hormone, while lower growth hormone in turn promotes greater fat storage: a potentially self-reinforcing cycle.

In centenarians, researchers sometimes observe slightly reduced thyroid hormone levels. The thinking is that a somewhat slower metabolism limits oxidative damage and thereby slows ageing. But in sick individuals, lower thyroid values are a sign of deterioration. This association has not yet been proven in randomised research; no recommendations can currently be based on it.

Metformin, a drug that improves insulin sensitivity and is used in diabetes, produces striking figures in a large summary of studies: diabetics who used it had 7 percent lower mortality than non-diabetics, and 28 percent lower mortality than diabetics on other treatments. Whether metformin also slows the ageing process in healthy people is currently being investigated, but has not yet been proven. Researchers caution that the figures found may partly be explained by selection effects.