Growth Hormone and IGF-1: Sleep, Exercise, Fasting and the Booster Myth

Growth hormone, or GH, is a protein hormone made by the pituitary gland, a small organ at the base of the brain. In children it controls growth in height; in adults it affects bone, muscle and the way the body uses fuel. Most of its growth effect is carried out by a second hormone, insulin-like growth factor 1 (IGF-1), which the liver makes when GH arrives. GH is released in bursts, so one blood value says little. Exercise can raise it by 300 to 500 per cent for a short while. This entry is part of NNWA's handbook of hormones.

What does growth hormone do, and where does IGF-1 fit?

GH is the signal and IGF-1 does much of the work. When GH enters the blood, the liver responds by producing IGF-1, and the US National Institutes of Health describe IGF-1 as the hormone that actually causes bones and body tissue to grow. In children this pair drives bone growth, muscle development and height. In adults GH goes on affecting bone and muscle health and helps control metabolism, the process of turning food into energy.

The two hormones behave differently in the blood. GH changes through the day with meals, activity and sleep, so a standard blood test for it is usually unhelpful. IGF-1 is far steadier, and for that reason doctors use it to track GH over time. IGF-1 is also sensitive to nutrition, which matters in a country where many children do not get enough to eat. That point returns in the Indian section below.

How does sleep change growth hormone?

Sleep is when the largest pulse arrives. In a classic study, blood was drawn every 30 minutes through 38 nights in eight young adults. In seven of them a GH peak lasting 1.5 to 3.5 hours appeared with the onset of deep sleep, and when sleep was delayed the peak was delayed with it. Volunteers who were woken for two to three hours and then went back to sleep produced a second peak.

Deep sleep shrinks with age, and GH goes with it. Pooled recordings from 149 healthy men aged 16 to 83 showed deep slow wave sleep falling from 18.9 per cent of the night in early adulthood to 3.4 per cent in midlife. GH secretion fell alongside it, by 372 micrograms per decade over that span, and the amount of GH was linked to the amount of deep sleep whatever the man's age. ICMR-NIN's Dietary Guidelines for Indians advise 6 to 8 hours of sleep a day.

What do exercise and fasting do?

Both raise GH, for different reasons. A Sports Medicine review calls sleep and exercise the most powerful stimuli that are not drugs. Intensity is the main factor: hard exercise, above what physiologists call the lactate threshold, for at least 10 minutes appears to give the greatest response, and resistance training also produces a clear rise. A later review puts the size of the rise at 300 to 500 per cent.

Fasting raises GH as part of the body's response to having no food. Six healthy men who fasted for five days went from 5.8 to 9.9 GH pulses in 24 hours, and their largest pulse rose from 5.9 to 12.3 ng/ml. At the same time IGF-1, then called somatomedin C, fell from 1.31 to 0.77 units per millilitre and blood glucose fell from 4.9 to 3.2 mmol/L. More GH with less IGF-1 is a sign of a body conserving fuel, not of extra growth.

How do protein and energy intake affect IGF-1?

Eating enough keeps IGF-1 up; eating too little brings it down. A review in Endocrine Reviews calls nutrition one of the main regulators of circulating IGF-1 and reports that energy or protein deprivation lowers it markedly in humans. Both are needed to restore it after a fast, and in adults energy may matter somewhat more than protein: below a threshold of energy intake, even an optimal protein intake fails to raise IGF-1. The fall happens independently of the changes in GH secretion that dieting brings.

The practical reading is plain. Adequate energy and adequate protein support normal IGF-1; extra protein on top of enough has not been shown, in the sources read for this entry, to push growth further. The protein calculator estimates a daily figure, the protein table for Indian foods shows where it comes from, and the handbook's entry on lysine in Indian diets explains why ICMR-NIN advises eating cereals and pulses together.

The Indian picture: stunting, growth charts and protein

Short stature in India is far more often about food and illness than about hormones. NFHS-5 found that 36 per cent of children under five are stunted, and describes stunting as a sign of chronic undernutrition. Among children whose mothers had no schooling the figure was 46 per cent, against 26 per cent where the mother had 12 or more years of schooling. ICMR-NIN's guidelines add that babies born small are at higher risk of stunting.

Growth hormone deficiency is a different and much rarer matter. At a referral endocrine clinic in Srinagar, 193 people with severe short stature, more than three standard deviations below the mean, were investigated over a decade. GH deficiency was the commonest identifiable cause, at 22.8 per cent, followed by normal variant short stature at 18.7 per cent; primary hypothyroidism and malnutrition accounted for 7.8 per cent each. Those are figures for children already referred to a specialist, not for children in general.

Height is judged on a chart, not by comparing cousins. The national academy of children's doctors, the IAP, revised its growth charts for ages 5 to 18 in 2015, using data on 33,148 children from 14 cities, and recommends WHO standards below five years. ICMR-NIN's 2020 report sets the protein allowances that growth needs, and its guidelines ask children and adolescents for at least 60 minutes of moderate to vigorous activity a day.

These amounts are meant to come from ordinary food: dal, milk, curd, egg, fish or meat where eaten, with rice or roti. ICMR-NIN's guidelines say plainly that protein powders are unnecessary for normal healthy life. NNWA's child nutrition diet chart lays out full days by age. The 2020 report adds that for people on cereal-based diets with low quality protein the requirement is 1 g per kg a day.

The booster myth: do amino acids that raise GH build muscle?

No. The products usually contain arginine, lysine or ornithine, and the claim rests on a real observation: these amino acids can stimulate GH release when infused or swallowed. A review of their use by athletes found the response highly variable, found that oral amounts large enough to release GH are likely to cause stomach discomfort and diarrhoea, and found no properly conducted study in which taking them before strength training increased muscle mass or strength beyond training alone. It did not recommend them.

Later evidence points the same way. Oral arginine before exercise gave a smaller GH rise than exercise alone, about 200 per cent against 300 to 500. The International Society of Sports Nutrition's review of supplements concludes that there is no convincing scientific evidence that secretagogues support increases in lean body mass or muscular performance. ICMR-NIN states that protein supplements taken on top of a balanced diet are not going to build more muscle.

A worked example: the booster arithmetic

This is an illustrative case, not a real person. A 24-year-old vegetarian in Pune weighs 70 kg, lifts four days a week, sleeps about five and a half hours and is considering an arginine product sold as a natural GH booster.

The decision in this example is to skip the product, eat to the protein figure and sleep longer. NNWA's article on an Indian diet for muscle gain covers the food side, and the handbook's entry on creatine covers a supplement whose evidence for strength is of a different order.

Which tests look at growth hormone?

Because GH comes in pulses, doctors rarely rely on a single GH value. They measure IGF-1, which is steadier, and they test how the pituitary responds when it is pushed or held back. The Endocrine Society's guideline on adult GH deficiency says that confirmation through stimulation testing is usually required. What a result means depends on age and on the rest of the clinical picture, so interpretation belongs to an endocrinologist or, for a child, a paediatric endocrinologist.

Is a short child a case for growth hormone?

That is a paediatrician's question, and usually the answer starts with a growth chart, not a hormone. The signs that lead doctors to test are a slowed rate of growth compared with children of the same age and sex, shorter height and limbs with lower weight, and delayed puberty. Many short children have none of these signs. Normal variant short stature and malnutrition were both on the Srinagar clinic's list, and the national stunting figure shows how common undernutrition is. No powder, tonic or amino acid sold for height has support in the sources read for this entry.

Misuse, risks and when to see a doctor

GH is a prescription medicine, given by injection for diagnosed deficiency, and decisions about it are made by specialists. Used by healthy people it does not deliver what is claimed. A systematic review of 27 study samples in fit young adults found that lean body mass rose by 2.1 kg, but strength and exercise capacity did not improve, and those given GH more often had soft tissue swelling and fatigue. Its authors concluded that claims of better performance are not supported by the scientific literature.

The disease of natural GH excess shows what long exposure does. In acromegaly, diagnosed in about 3 to 14 of every 100,000 people, the hands, feet and facial features enlarge, and the high IGF-1 changes how the body handles glucose and fats, which can lead to type 2 diabetes, high blood pressure and heart disease. For athletes there is a further point: the World Anti-Doping Agency prohibits GH, its fragments, its releasing hormones and GH secretagogues at all times. Nothing here is advice to take, change or stop a medicine.

Learning this with NNWA

Growth, sleep and training nutrition are part of what NNWA teaches. It is a private skill academy in Kolkata with online classes in English and Hindi, and the Sports Nutrition course and Child Nutrition course train people to advise healthy clients on food and to send medical questions to a doctor. Neither is a degree or a dietitian qualification.