The pubertal growth spurt is, in developmental terms, already the second growth spurt humans experience. The first happens in infancy, when babies roughly triple their birth weight and grow dramatically in their first two years. Growth then slows through childhood before surging again during puberty. A true third growth spurt after puberty does not occur because the biological machinery that allows rapid height gain shuts down permanently once the growth plates in your long bones fuse. That said, several real phenomena after puberty can make it feel as though another round of growing is happening, and some skeletal changes genuinely do continue well into adulthood.
Infancy, Childhood, and Puberty as Separate Growth Phases
Human growth follows a well-documented three-phase pattern. The first phase is infancy, when growth velocity is highest. A healthy infant typically grows around 25 centimeters in the first year alone. That pace drops sharply, and from roughly age two until the onset of puberty, children grow at a steadier, slower rate of about five to seven centimeters per year. This middle stretch is sometimes called the “childhood growth plateau,” and it is the period when kids and their parents are least likely to notice changes in height from month to month.
The second major surge arrives with puberty. In girls, peak growth velocity usually hits around age 11 to 12; in boys, it comes a couple of years later, typically around 13 to 14. During this window, teenagers can add eight to twelve centimeters per year at the peak. The hormonal cocktail driving this includes growth hormone, insulin-like growth factor 1 (IGF-1), and sex steroids like estrogen and testosterone, all of which ramp up together and amplify each other’s effects on bone elongation, muscle mass, and skeletal mineralization.1Hormone Research. Sex Steroids, Growth Hormone, Insulin-Like Growth Factor-1: Neuroendocrine and Metabolic Regulation in Puberty Body composition changes, including shifts in fat distribution, feed signals back to the hormonal system and shape the timing and intensity of the spurt.2PubMed. Growth at puberty
When people search for a “second growth spurt,” they usually mean a second surge after puberty has already begun or ended. Understanding that puberty itself is biologically the second surge helps clarify why a third one would require the body to reverse a process that is, by design, one-way.
Why Growth Stops and Cannot Restart
Height growth depends on the growth plates, strips of cartilage near the ends of long bones. During childhood and puberty, cells in these plates divide, stack up, enlarge, and gradually get replaced by hard bone. This process is what physically adds length to your legs, arms, and spine. But the system has a built-in expiration. As puberty progresses, rising levels of estrogen (in both sexes, not just females) gradually exhaust the cartilage cells’ ability to keep dividing. Eventually the remaining cartilage is fully replaced by bone in an abrupt event called epiphyseal fusion.3Trends in Endocrinology & Metabolism. Growth Plate Senescence and Epiphyseal Fusion Once a growth plate fuses, longitudinal growth at that site is permanently finished.4Endocrine Reviews. Systemic and Local Regulation of the Growth Plate
The process does not happen at every bone simultaneously. Growth plates in the hands and feet tend to close first, often by mid-to-late puberty. Plates in the legs and spine close somewhat later. The last plates to fuse are usually in the clavicle (collarbone) and the spine, sometimes not until the early to mid-twenties. After fusion, the cartilage is replaced by calcified bone and the growth plate itself ceases to exist.5PubMed Central. Growth plate closure and therapeutic interventions No diet, exercise program, supplement, or stretching routine can reopen a fused growth plate.
Late Puberty and Catch-Up Growth
One of the most common reasons people believe they had a “second growth spurt” is that their pubertal growth arrived later than average. A boy who barely grew through his early teens while his classmates shot up, then suddenly gained several inches at 16 or 17, did not have two growth spurts. He had one delayed spurt. The end result is often a normal adult height, because the growth plates stayed open longer, giving the body more time to accumulate height even though puberty started late.
Research on boys with late-normal puberty shows that this catch-up can be substantial. Not only does linear bone growth continue longer, but bone thickness and bone density also catch up by young adulthood, leaving little measurable deficit compared to boys who went through puberty on a more typical timeline.6PubMed Central. Malnutrition and Catch-Up Growth during Childhood and Puberty A similar pattern has been documented in children with certain metabolic conditions that delay growth in early childhood. In boys with a specific type of glycogen storage disease, for instance, researchers found significant growth retardation between ages two and ten, followed by a late pubertal growth spurt that brought them to near-normal adult height.7PubMed. Characteristic growth pattern in male X-linked phosphorylase-b kinase deficiency (GSD IX)
The psychological experience of late bloomers is worth acknowledging. If you spent years being the shortest person in your friend group and then grew rapidly in your late teens, it genuinely felt like a sudden, unexpected event. But the underlying biology was the same single pubertal growth spurt everyone gets, just shifted later on the calendar.
Skeletal Changes That Continue After Growth Plates Close
Although you stop getting taller once your growth plates fuse, your skeleton is not entirely done changing. Several bones continue to remodel in measurable ways through your twenties and beyond, and understanding these changes helps explain why some young adults feel like their bodies are still “growing.”
The clavicle is a standout example. A study tracking clavicle length across adolescence and early adulthood found that the bone kept adding length even into the early twenties. In males aged 20 to 25, clavicular growth still averaged about 1.7 millimeters per year. In females the same age, growth slowed to a near standstill but had not fully stopped. The researchers noted they could not identify a definitive age of terminal clavicular growth in either sex because growth was still ongoing in most patients in the oldest group studied.8PubMed. The Clavicle Continues to Grow During Adolescence and Early Adulthood Broader shoulders in a 22-year-old compared to when they were 18 are not imaginary; the clavicle really is still getting longer.
The pelvis widens too, and it keeps doing so well past skeletal maturity. A cross-sectional study using CT scans found that the bony pelvis widens by more than 20 millimeters between the ages of 20 and 80, with the effect appearing in both men and women. The width increase showed up at multiple landmarks, including the distance between the hip joints and between the tops of the iliac wings. The lower lumbar spine also grew wider over the same period.9PubMed. Surprising evidence of pelvic growth (widening) after skeletal maturity This is not the kind of change that adds height, but it does alter body proportions in ways that can make someone feel like they are still “filling out.”
Bone density is another piece of the puzzle. While height stops increasing when long-bone growth plates fuse (typically by the late teens in women and early twenties in men), the skeleton keeps getting denser and heavier for years afterward. Total body bone mineral density reaches about 99% of its peak around age 22 in women, and total bone mineral content peaks a few years later, around age 26.10PubMed. Peak bone mass in young women In men, the trajectory is similar, with peak bone density arriving in the early to late twenties.11PubMed Central. Peak Bone Mass and Patterns of Change in Total Bone Mineral Density and Bone Mineral Contents From Childhood Into Young Adulthood So even though you are not getting taller, your bones are genuinely getting stronger and heavier throughout your twenties, and that can subtly affect how your body feels and looks.
Your Face Keeps Changing Too
Adults who look at photos of themselves at 18 and again at 30 often notice that their face looks different in ways that go beyond weight gain or loss. That is because craniofacial bones continue to remodel through adulthood. Longitudinal studies tracking facial structure from late adolescence through midlife found significant increases in the length of the midface and the height of the lower face during the twenties and thirties. These changes were more pronounced in women than in men. Soft-tissue changes were even more noticeable, including thinning and lengthening of the upper lip and drooping of the nasal tip.12PubMed. The aging craniofacial complex: a longitudinal cephalometric study from late adolescence to late adulthood A separate study focused on the third decade of life specifically found that total anterior face height increased in both sexes, with lower face height growing more in women.13PubMed. Natural craniofacial changes in the third decade of life: a longitudinal study
Then there is cartilage. Ears and noses are made largely of cartilage, which does not stop changing with age. A study measuring ear size across the adult lifespan found that ear circumference increases on average about half a millimeter per year, likely because of age-related changes in collagen structure.14PubMed. Ear size as a predictor of chronological age This is not a “growth spurt” by any stretch, but it is genuine, ongoing physical change that adds up over decades.
Things That Mimic Growth but Are Not Growth
Some experiences people describe as a “second growth spurt” are actually reversible or non-skeletal changes that make the body temporarily or permanently different in size without any new bone growth happening.
Your height fluctuates by one to two centimeters every single day. The discs between your vertebrae act like sponges: during the day, weight-bearing compresses them and pushes fluid out. Overnight, when you are lying down, the discs reabsorb fluid and swell back up. The diurnal height loss from disc compression can range from about 13 to 21 millimeters.15PubMed. Diurnal fluid changes of lumbar discs measured indirectly by magnetic resonance imaging Disc height can vary by about 10% between morning and evening.16PubMed. Diurnal variations in intervertebral disc height affect spine flexibility, intradiscal pressure and contact compressive forces in the facet joints If you happen to measure yourself first thing in the morning after a long sleep, you may find yourself taller than you expected. That is real, but it reverses by bedtime.
Foot size changes during pregnancy are another common example. The added body weight combined with hormonal loosening of ligaments can flatten the arches permanently, leading to a measurable increase in foot length. Research found that arch height and stiffness dropped significantly during pregnancy, with the first pregnancy having the most dramatic effect.17PubMed Central. Pregnancy leads to lasting changes in foot structure Going up a shoe size after having a baby is not a growth spurt. It is a structural change in soft tissue and ligaments. But it is permanent and it is real.
Posture improvement can also make a noticeable difference. A young adult who starts strength training and corrects a rounded-shoulders posture may genuinely measure a centimeter or two taller at the doctor’s office. No new bone was created; the existing spine is simply being held in better alignment. Similarly, weight loss can improve spinal alignment by reducing compression forces on the discs.
Medical Interventions That Extend the Growth Window
For children and adolescents diagnosed with growth hormone deficiency or other conditions that limit height, medical treatment can extend or amplify the pubertal growth spurt. Growth hormone therapy directly increases the rate at which bones elongate, and in some cases it is combined with aromatase inhibitors, drugs that reduce the conversion of testosterone to estrogen. Since estrogen is the primary signal that triggers growth plate fusion, lowering estrogen levels can delay that fusion and keep the growth window open longer.
A randomized trial of pubertal boys with idiopathic short stature tested aromatase inhibitors alone, growth hormone alone, and the combination. Over 24 months, the combination group gained about 19 centimeters in height compared to roughly 14 centimeters in the aromatase-inhibitor-only group.18PubMed Central. Randomized Trial of Aromatase Inhibitors, Growth Hormone, or Combination in Pubertal Boys with Idiopathic, Short Stature These therapies only work while growth plates are still open. They are not tools for adding height to fully grown adults, and they carry side effects that make them inappropriate outside of genuine medical need.
There are also cases where specific genetic mutations affect the growth plate directly. In patients with mutations in the ACAN gene (which encodes a key cartilage protein), growth hormone combined with aromatase inhibitors has been used to improve adult height by both speeding growth velocity and extending the time before fusion.19AACE Endocrinology and Diabetes. Adult Height After Growth Hormone and Aromatase Inhibitor Therapy for Short Stature due to ACAN Mutation These are highly specialized treatments prescribed on a case-by-case basis, but they illustrate the principle: once the growth plates are gone, there is no pharmacological way to restart longitudinal bone growth.
Genetics of Growth Spurt Timing
Why some teenagers shoot up at 12 while others wait until 16 is partly a matter of genetics. Genome-wide association studies have identified specific gene variants linked not just to adult height, but specifically to the timing and intensity of the pubertal growth spurt. Researchers studying a Finnish birth cohort identified variants near genes like SOCS2, CDK6, and CABLES1 that were associated with the age at which peak growth velocity occurred during puberty.20PLoS Genetics. Genetic Determinants of Height Growth Assessed Longitudinally from Infancy to Adulthood in the Northern Finland Birth Cohort 1966 A larger trans-ancestral study identified 26 regions of the genome linked to pubertal height growth patterns, confirming that growth spurt timing has a strong heritable component that operates across different ethnic backgrounds.21PubMed. Trans-ancestral genome-wide association study of longitudinal pubertal height growth and shared heritability with adult health outcomes
This matters for the “second growth spurt” question because many of the gene variants that determine when you hit your pubertal growth spurt also correlate with adult height. If your genetic profile codes for a late spurt, you are more likely to keep growing into your late teens while your early-maturing friends stopped at 15. Two siblings in the same family can have visibly different growth trajectories simply because they inherited different combinations of these variants. The end result may be similar adult heights, but the paths getting there look completely different, and the late bloomer’s path can easily be misread as a mysterious “second” spurt.
The Adolescent Growth Spurt in Evolutionary Context
The human adolescent growth spurt has long been described as something unique among primates, a distinct and dramatic acceleration in growth that other species supposedly lack. Recent comparative research has challenged that view. A 2023 study published in eLife compared growth patterns in humans and bonobos at equivalent developmental scales and found that bonobo adolescents show similar changes in weight and length growth rates that correspond well with each other. The researchers concluded that the proposed general uniqueness of the human adolescent growth spurt in length growth “can be rebutted.”22PubMed Central. Evolutionary biology behind human extended brain growth and late-maturing skeletal traits compared to non-human primates
What does appear distinctive about humans is not the growth spurt itself but its timing relative to other developmental milestones. Humans have an unusually extended period of brain growth and delayed skeletal maturation compared to other primates. Our growth plates stay open longer, our bone density peaks later, and our brains continue developing into the mid-twenties. This extended developmental timeline is likely what creates the perception that growth “should” still be happening in the late teens and early twenties. Biologically, many systems are still maturing during that period. Height growth just is not one of them for most people.
When to Worry and When to Wait
Parents of teenagers who seem to have stalled in their growth often wonder whether something is wrong. The honest answer is that most of the time, the child is simply on a later timeline. Constitutional delay of growth and puberty, the medical term for being a late bloomer, is the most common cause of short stature in adolescents and is not a disease. These kids eventually reach a normal adult height without any treatment.
Red flags that do warrant medical evaluation include complete absence of any pubertal signs by age 14 in boys or 13 in girls, a dramatic drop-off in growth rate before puberty has begun, and disproportionate growth where limbs and torso are growing at very different rates. A pediatric endocrinologist can assess bone age using an X-ray of the hand and wrist to determine how much growth potential remains. If the growth plates are still wide open despite a late start, that is generally reassuring. If they are prematurely fusing, that points to a different problem that may benefit from intervention.
For adults in their twenties who swear they just grew half an inch, the most likely explanations are improved posture, measurement variability (time of day, shoes, how carefully the measurement was taken), or the ongoing clavicle and pelvic changes described above. Genuine height gain from new bone growth after age 20 is vanishingly rare in people with normal hormonal function and would typically point to a medical condition like acromegaly, where the pituitary gland overproduces growth hormone. In that case, the “growth” involves thickening of bones and soft tissues rather than elongation of long bones, since the growth plates are already fused.