Your height is the result of your bones physically lengthening during childhood and adolescence, driven by a combination of genetics, hormones, and nutrition. About 80% of your final height is determined by the DNA you inherited from your parents, with the remaining 20% shaped by environmental factors like diet and overall health during your growing years. The process is active from birth until your growth plates seal shut, typically between ages 13 and 17 depending on sex.
How Bones Actually Get Longer
Height comes from the lengthening of your long bones, particularly in your legs and spine. Near the ends of every long bone in a child’s body sits a strip of cartilage called a growth plate. This is where all the action happens.
The process works like a slow conveyor belt. On one side of the growth plate, cartilage cells actively divide and multiply, creating new cartilage tissue. On the other side, older cartilage cells degenerate and get replaced by bone-building cells that harden the cartilage into solid bone. As long as new cartilage is being produced faster than old cartilage is being converted to bone, the bone keeps getting longer and you keep getting taller. This cycle repeats continuously throughout childhood, with periods of faster and slower growth, until the plates eventually close.
The Hormonal System That Controls Growth
Your pituitary gland, a pea-sized structure at the base of your brain, releases growth hormone in pulses throughout the day (especially during deep sleep). Growth hormone doesn’t stretch your bones directly. Instead, it signals your liver to produce a secondary messenger called IGF-1, which travels through the bloodstream and stimulates the cartilage cells in your growth plates to divide. Growth hormone also acts on those cartilage cells directly, prompting them to release their own local IGF-1 for an additional boost.
The net effect is increased protein production, faster cell division, and less cell death in the growth plates. This is why children with growth hormone deficiency grow significantly slower than their peers, and why the hormone’s activity peaks during the rapid growth spurts of infancy and puberty.
Estrogen: The Signal That Stops Growth
Puberty introduces a paradox. Early in puberty, rising estrogen levels at low concentrations actually stimulate growth, contributing to the adolescent growth spurt. But as puberty progresses and estrogen levels climb higher, the same hormone reverses course and triggers the permanent closure of the growth plates. Estrogen acts directly on cartilage cells, causing them to stop dividing and the remaining cartilage to fully harden into bone.
This happens in both boys and girls. It’s estrogen, not testosterone, that seals the growth plates in males too (boys produce estrogen in smaller amounts converted from testosterone). This is why girls, who enter puberty earlier and reach high estrogen levels sooner, generally stop growing around ages 13 to 15, while boys typically keep growing until 15 to 17. Once the plates are fully fused, no amount of growth hormone can make bones longer. Your adult height is locked in.
Why Genetics Matters So Much
Scientists estimate that roughly 80% of the variation in height between people comes down to genetics. But height isn’t controlled by one or two genes. Hundreds of genetic variants each contribute a small amount, nudging your final height slightly taller or shorter. Some variants affect how much growth hormone your body produces. Others influence how sensitive your cartilage cells are to growth signals, how quickly your growth plates mature, or how your skeleton proportions develop.
A few rare gene variants have outsized effects. Mutations in the gene responsible for a key growth factor receptor cause achondroplasia, the most common form of dwarfism. Variants in another gene cause Marfan syndrome, which leads to unusually tall stature and long limbs. But for the vast majority of people, height is the cumulative result of many small genetic contributions, which is why most people’s heights fall within a predictable range based on their parents. A common rule of thumb is to average both parents’ heights (adjusting up for boys, down for girls), and expect the child to land within a few inches of that number.
What Nutrition and Environment Contribute
That remaining 20% of height variation comes largely from nutrition, particularly during the first five years of life and again during puberty. The relationship is straightforward: bones need raw materials to grow, and a body under nutritional stress will prioritize survival over reaching its full genetic height potential.
Calcium and vitamin D appear to be especially critical. A study of children aged 2 to 5 found that stunted children had significantly lower intake of calcium, vitamin D, and several nutrients commonly found in milk, even when their overall calorie and protein intake was adequate. Children getting only about 15 to 21% of the recommended intake of vitamin D and calcium showed stunting rates as high as 49% in the 4 to 5 year old age group. This suggests that simply eating enough food isn’t sufficient. The specific nutrients that support bone mineralization matter enormously.
Chronic illness, severe stress, and lack of sleep during childhood can also suppress growth, largely by disrupting the hormonal signaling described above. Growth hormone is released primarily during deep sleep, so children who consistently sleep poorly may not produce enough to support normal growth.
How Much Height Varies Around the World
Global height data reveals just how powerfully environment interacts with genetics across populations. Dutch men born in 1996 are the tallest on Earth, averaging 182.5 cm (about 6 feet). Men in Belgium, Estonia, Latvia, and Denmark aren’t far behind at over 181 cm. The tallest women live in Latvia, the Netherlands, Estonia, and the Czech Republic, averaging above 168 cm (about 5 feet 6 inches).
At the other end of the spectrum, men in Timor-Leste, Yemen, and Laos average only about 160 cm (5 feet 3 inches), a gap of 22 to 23 cm from the tallest countries. Women in Guatemala average just 149.4 cm (under 4 feet 11 inches), with similarly short averages in the Philippines, Bangladesh, and Nepal. These differences reflect generations of varying nutrition, healthcare access, and disease burden layered on top of genetic diversity. Over the past century, populations with improving living conditions have gotten dramatically taller, while those facing persistent poverty have seen much smaller gains.
When Growth Falls Outside the Normal Range
Pediatricians track height on standardized growth charts and look for red flags: a child consistently falling well below the expected range for their age, growing much shorter than their parents’ heights would predict, or showing a sudden slowdown in growth velocity. A child whose height falls more than 1.5 standard deviations below what would be expected given their parents’ heights may be evaluated for growth hormone deficiency.
Testing for growth hormone deficiency involves stimulating the pituitary gland and measuring the hormone response, though the exact threshold used to define deficiency varies by country and remains somewhat debated among specialists. Doctors also check for skeletal disproportion, since certain genetic conditions affect limb and trunk growth differently rather than reducing height uniformly. For children identified early, treatment with growth hormone can meaningfully increase adult height, but it only works while growth plates remain open. Timing matters.