Adult height is the maximum vertical stature achieved once the skeletal system has fully matured. By the time a person reaches their early twenties, the biological processes responsible for increasing bone length have typically concluded. Understanding the mechanics of human bone growth reveals why significant height gain is impossible after this point.
The Biological Basis of Adult Height
The ability to grow taller relies on specialized structures called epiphyseal plates, or growth plates. These plates are cartilage located near the ends of long bones. New bone is generated through endochondral ossification, where cartilage cells divide and are replaced by hard bone tissue, thereby lengthening the bone.
During puberty, increasing levels of sex hormones signal epiphyseal fusion. This hormonal surge accelerates the rate at which cartilage is replaced by bone, leading to the complete disappearance of the growth plate. Once fusion is complete, the cartilage is entirely converted into solid bone, leaving behind only a faint epiphyseal line.
The timing of this closure varies, but for most people, all growth plates are fused by the late teens or early twenties. Girls typically complete this process around age 16, while boys often continue growing until about age 19, with final plates closing no later than 22 years of age. Once this transformation is finished, the long bones cannot increase in length, making true vertical growth impossible.
Factors That Determine Maximum Height
Final height is determined by genetic and environmental influences established during childhood and adolescence. Genetics is the largest determinant, accounting for an estimated 80% to 90% of a person’s final stature. Hundreds of different gene variations contribute to this polygenic trait, setting the biological blueprint for potential height.
Hormonal signaling regulates how closely a person reaches their genetic potential. Key hormones include Growth Hormone, secreted by the pituitary gland, and thyroid hormones, which are necessary for proper bone and tissue development. Sex hormones drive the rapid growth spurt during puberty but ultimately trigger the closure of the growth plates, halting growth.
Environmental factors, particularly early life nutrition and overall health, account for the remaining percentage of height determination. A diet rich in essential nutrients provides the necessary building blocks for bone development. Chronic poor nutrition or recurrent illness can prevent the body from reaching its genetic potential.
Height Changes That Are Not Growth
While true bone lengthening stops once the growth plates fuse, adults experience temporary fluctuations in measured height. These changes are due to the state of the intervertebral discs in the spine. The spine is composed of vertebrae separated by these soft, fluid-filled cushions that provide shock absorption.
Throughout the day, gravity and activity cause the spine to compress, squeezing fluid out of the discs. This diurnal compression can result in a height loss of up to 1 to 2 centimeters (about 0.5 to 0.75 inches) between morning and evening. Sleeping allows the discs to decompress and rehydrate, temporarily restoring maximum height upon waking.
Another non-growth factor affecting stature is posture, which influences perceived height. Poor posture, such as chronic slouching, leads to functional height loss by compressing the spine. Correcting poor posture, often through core strengthening, can restore the spine to its natural alignment. This correction can make a person stand taller by regaining the height lost to habitual slouching.