For better or worse, the quality and quantity of our sleep directly and profoundly influence our hormones, and therefore our mental health, weight, and immunity. Melatonin, thyroid stimulating hormone, cortisol, insulin and many other hormones fluctuate across the day and night and are highly regulated by our circadian and sleep-wake cycles. Hence their reliance on regular, quality sleep to do what they are supposed to and help you be at your best.
It’s a vicious circle. Sleep deprivation throws hormone levels out of balance, which in turn causes more sleep deprivation. Getting enough sleep is vital, not just for your short-term energy levels but for the normal function of these important hormones.
Leptin – the satiety hormone – has an important role in maintaining a healthy weight. Its job is to suppress the appetite and tell the body when it's full, and time to stop eating. Sleep deprivation lowers leptin, making you feel hungrier.
This hormone is also related to hunger and appetite. Ghrelin stimulates the appetite and tells the body that it's time to eat. Leptin and Ghrelin act like a seesaw. While leptin levels fall due to lack of sleep, ghrelin rises, making you even more peckish. This is a key reason why sleep deprivation is associated with weight gain.
Lack of sleep causes adrenal stress and creates cellular resistance to insulin. A 2005 study showed that people with sleep deprivation show insulin abnormalities, which leads to suboptimal glucose processing. If left unchecked, the risk of type 2 diabetes increases.
Sleep deprivation ramps up thyroid stimulating hormone (TSH). High levels of TSH can slow the metabolism, and lead to hair loss, fatigue, feeling chilly, and cold extremities
Cortisol and melatonin
An example of another hormone seesaw: when melatonin is high, cortisol should be low and vice versa. A sleep deprived body is by definition in a state of stress – causing your adrenal glands to produce more cortisol (aka ‘the stress hormone’). High cortisol levels block the rise of melatonin, preventing you falling asleep or being able to stay asleep. This vicious circle causes that 'wired and tired' feeling – of exhaustion plus trouble getting to sleep.
Your sex hormones can also be affected by sleep deprivation. When you’re stressed (see cortisol section above), the last thing your body wants to do is bring a baby into a world it perceives as dangerous. So it reduces production of sex hormones including oestrogen, testosterone, and progesterone. Outside the bedroom, lack of sleep affects testosterone, which can result in low energy and libido, and difficulty concentrating.