Biology
Human Growth
Quick fact
The fastest period of human growth occurs before birth: in the nine months of gestation, a single cell multiplies into a trillion cells and grows from microscopic to about 50 cm long.
Why this is interesting
We all grow taller as children, but why does growth stop after adolescence? The answer lies in a tiny, hidden layer inside your bones.
Read the full explanation
Understanding Human Growth
Human growth is not steady; it follows a predictable pattern. Infants grow rapidly, then the pace slows during childhood. At puberty, a surge of sex hormones triggers a dramatic growth spurt, especially in height. This spurt happens because the long bones of the legs and arms lengthen at specialized regions called epiphyseal plates, or growth plates. These plates are made of cartilage that gradually turns into bone. After the spurt, the same hormones eventually cause the plates to fuse (ossify), stopping further lengthening. This is why adults do not get taller, though other tissues can still grow or change.
A deeper explanation
The central mechanism of human height growth is the activity of the epiphyseal plates. These plates are located near the ends of long bones. They consist of layers of proliferating chondrocytes (cartilage cells) that produce new cartilage, which is then replaced by bone in a process called endochondral ossification. Growth hormone (GH), released by the pituitary gland, stimulates the liver to produce insulin-like growth factor 1 (IGF-1). GH and IGF-1 work together to promote cell division and protein synthesis throughout the body, including at the growth plates. At puberty, rising levels of estrogen (in both sexes) and testosterone accelerate growth further but also initiate the eventual fusion of the epiphyseal plates. Once the plates fuse, no further length increase is possible. The timing of these events is genetically programmed but can be influenced by nutrition, health, and other factors. Understanding this process explains why growth disorders can occur, such as gigantism (excess GH) or dwarfism (GH deficiency), and why nutrition in childhood is critical for reaching full adult height.