The physical process of growing taller is a finite period in human development, concluding for most people in the late teens. However, for individuals termed “late bloomers,” the timeline for growth is significantly extended. The age at which a late bloomer stops growing is directly tied to the delayed timing of their puberty, which allows for a longer overall period of growth before skeletal maturity is reached. Understanding this delayed process requires looking into the biological mechanisms that control the onset and conclusion of growth.
Understanding Constitutional Delay of Growth and Puberty
The term “late bloomer” is often used to describe someone whose physical development lags behind their peers, but medically, this condition is known as Constitutional Delay of Growth and Puberty (CDGP). CDGP is not considered a disease but rather a variation of normal development, frequently passed down through families. Affected children are typically shorter than average during childhood because their growth rate slows down temporarily, and they start puberty later than the typical age range.
This delay means that while children with CDGP may be the shortest in their class, they are otherwise healthy and follow a normal pattern of development on a postponed schedule. CDGP is diagnosed when a child’s pubertal signs are absent by age 13 for girls or age 14 for boys, and it is the most common cause of delayed puberty. Since this is a delay in the body’s internal clock, the ultimate prognosis for final adult height is usually good, aligning with the expected height based on family genetics.
The Mechanism of Growth Cessation
Longitudinal growth in humans occurs primarily at the growth plates, also known as epiphyseal plates, located at the ends of long bones. These plates are made of cartilage cells, called chondrocytes, which multiply, enlarge, and then are replaced by bone tissue, causing the bone to lengthen. This continuous process allows a person to grow taller throughout childhood and adolescence.
The eventual cessation of growth is triggered by the rise of sex hormones during puberty, specifically estrogen in both sexes. While testosterone is the primary male sex hormone, it is converted into estrogen in bone tissue, and this estrogen is the main catalyst for the maturation and closure of the growth plates. When sufficient estrogen is present, it causes the cartilage cells in the growth plates to stop multiplying and completely ossify, or fuse, into solid bone. Once this fusion, known as epiphyseal closure, is complete, no further increase in height is physically possible.
When Late Bloomers Reach Final Height
Since the onset of puberty, and thus the surge of sex hormones, is postponed in late bloomers, the growth plates remain open and active for a longer duration. This delayed timing directly translates to a more extended period of height gain compared to their peers who begin puberty on a typical schedule. For the general population, girls typically complete their growth between ages 14 and 16, and boys generally stop growing by ages 16 to 18.
In contrast, late bloomers, particularly males who constitute the majority of CDGP cases, often continue their growth well beyond the typical timeframe. Boys with CDGP commonly experience their pubertal growth spurt and continue growing into their late teens, often until age 18 to 21. This prolonged growth window allows late bloomers to “catch up” in height, ultimately reaching an adult height that is within the range predicted by their genetic potential.
Assessing Growth Potential and Prognosis
Medical professionals rely on a tool called “bone age” to assess the skeletal maturity and predict the final adult height of a late bloomer. Bone age is determined by taking a simple X-ray of the left hand and wrist, which reveals the degree of development in the bones compared to standardized reference images. For individuals with CDGP, the bone age is typically delayed by at least two years, often by two to four years, compared to their chronological age.
A delayed bone age is a positive indication because it confirms that the growth plates have not yet fused and that a significant amount of growth time remains. By using the bone age, doctors can project a more accurate final adult height than by relying solely on the child’s current height and chronological age. This assessment helps confirm the prognosis that the individual is simply developing later, and will eventually achieve an adult stature in line with their family’s height range.