The Science of Adolescent Growth
Growth in height is primarily a function of the growth plates (physes), areas of cartilage at the ends of long bones. During puberty, hormones like human growth hormone and sex steroids stimulate these plates to produce new bone, leading to increased bone length and a significant growth spurt.
Why Growth Stops: The Role of Fused Growth Plates
As puberty progresses, sex hormones cause the growth plates to harden and fuse. Once fused, the long bones can no longer lengthen, and height growth stops. In males, this typically occurs between 16 and 18, and in females, between 14 and 16. By 18, most people's growth plates are fused, making a second growth spurt impossible. Any minimal growth beyond this age, often less than an inch, is usually a final phase before complete fusion, not a second spurt.
Understanding the "Late Bloomer" Phenomenon
Constitutional growth delay, or being a "late bloomer," means puberty and the associated growth spurt start later than average. This is a normal variation, often genetic, where growth continues into the late teens or early twenties as their delayed growth plates fuse. They still reach a normal adult height, but later than their peers. A late bloomer's continued growth after 18 is part of their original, delayed pubertal growth, not a second spurt.
The Difference Between Growth and Development
While height growth typically ends after growth plate fusion, other forms of physical development, such as muscle mass increase in men, continue into the 20s and beyond. The term "second puberty" sometimes used to describe age-related body changes is not related to adolescent height growth.
When to Consult a Doctor
While rare, abnormal growth in adulthood can be a symptom of conditions like acromegaly, caused by excessive growth hormone production due to a pituitary gland disorder. This is a medical issue, not a natural growth spurt, and requires medical evaluation.
Comparison: Late Bloomer vs. Average Maturation
| Feature | Late Bloomer (Constitutional Delay) | Average Maturation |
|---|---|---|
| Puberty Onset | Later than peers (e.g., after 14 for boys) | Normal range for age (e.g., 9-14 for boys) |
| Growth Spurt | Delayed until mid-to-late teens | Occurs earlier, usually mid-teens |
| Final Height | Reached later, often around 18-21 | Reached by around 18 for most males, earlier for females |
| Growth Plates | Fuse at a later chronological age | Fuse within the typical age range |
| Long-Term Outcome | Reaches normal adult height, just later | Reaches normal adult height in typical timeframe |
Conclusion: The Final Say on Post-18 Growth
The concept of a second growth spurt at 18 or later is a myth. Height growth is limited by the fusion of growth plates during puberty. While late bloomers may grow slightly past 18, this is a continuation of their single, delayed pubertal growth spurt. Genetic factors largely determine height potential. A healthy lifestyle supports overall health and bone density but cannot increase height after growth plate fusion. For more information on adolescent development, consult resources like the National Center for Biotechnology Information (https://www.ncbi.nlm.nih.gov/).
