Puberty blockers do not stop height growth. They slow it down. Adolescents on these medications continue to grow, but at a rate closer to what you’d see in a child who hasn’t entered puberty yet. In one study of 50 transgender youth treated with blockers starting at early puberty stages, the median growth rate was about 5.1 centimeters (2 inches) per year, which was not significantly different from pre-pubertal children of the same age.
The more important effect is what happens to long-term height potential. Because puberty blockers delay the process that eventually seals off growth plates in your bones, they actually preserve the window for future growth rather than closing it.
How Growth Plates and Puberty Are Connected
Your bones grow longer from areas near their ends called growth plates. These plates are made of cartilage cells that keep dividing and turning into bone throughout childhood and adolescence. Eventually, they stop dividing and harden completely, which is when you reach your final adult height.
The signal that triggers growth plates to close is estrogen. This is true regardless of sex: in all bodies, estrogen accelerates the exhaustion of the dividing cells in growth plates and advances what researchers call “growth plate senescence.” During typical puberty, rising levels of sex hormones (testosterone in males, estrogen in females) fuel a growth spurt but also start the countdown toward those plates fusing shut. Testosterone contributes indirectly because the body converts some of it into estrogen.
Puberty blockers (GnRH agonists) work by desensitizing the pituitary gland so it stops signaling the ovaries or testes to produce sex hormones. With estrogen and testosterone suppressed, growth plate closure is postponed. Growth continues, just without the hormonal acceleration of a pubertal growth spurt.
What Happens to Growth Rate During Treatment
Once blockers take effect, growth velocity slows noticeably. In a study of transgender boys (those assigned female at birth), height increased by an average of 8.6 centimeters over the entire puberty-suppressive phase, which typically lasted around 1.5 to 2.5 years. That’s a meaningful amount of growth, but it’s slower than what peers going through puberty experience during their growth spurts.
Research on children treated with blockers for central precocious puberty (a condition where puberty starts abnormally early) shows a similar pattern: growth velocity tends to be highest in the first six months after starting treatment, then gradually declines. This mirrors the pre-pubertal growth rate, when children typically grow steadily but without the dramatic spurts of adolescence. Height doesn’t plateau or stop. It just proceeds at a gentler pace.
Final Adult Height After Blockers
The question most families really want answered is whether blockers compromise final adult height. The data is reassuring on this point.
A study of transgender girls (assigned male at birth) who were treated with blockers followed by estrogen found that their adult height averaged 180.4 centimeters (about 5 feet 11 inches). This was within 1.5 centimeters of what had been predicted at the start of treatment, and the small gap was attributed to the prediction method itself tending to overestimate height in the general population, not to the medication. Final height was not significantly different from their genetic target height based on parental stature.
For transgender boys treated with blockers followed by testosterone, the picture was similar. Growth decelerated during the suppressive phase but then accelerated once testosterone was introduced. From the start of hormone therapy, these individuals grew an additional 5 centimeters on average, reaching an adult height of about 172 centimeters (5 feet 8 inches). Their final height closely matched predictions made at the start of hormone therapy, with an average difference of just 0.2 centimeters.
The key mechanism here is that blockers keep the growth plates open. Once sex hormones are introduced, whether the body’s own (if blockers are stopped) or through hormone therapy, a growth spurt follows and bone maturation resumes on a more typical timeline.
The Growth Spurt Happens Later, Not Never
One way to think about it: puberty blockers shift the growth timeline rather than shrinking it. The pubertal growth spurt is delayed, not deleted. Clinical guidelines from WPATH note that during blocker treatment in early-pubertal adolescents, bone growth plates remain unfused. Once sex hormone treatment begins, “a growth spurt can occur, and bone maturation continues.” This is distinct from starting hormones in older adolescents whose growth plates have already closed, where no further height change would be expected regardless of treatment.
In the transgender boy cohort, researchers specifically observed “catch-up growth” during testosterone treatment that compensated for the slower growth during suppression. The rate at which testosterone doses were increased (faster versus slower) did not appear to change the total amount of height gained.
Bone Density Is a Separate Concern
While height itself is largely preserved, bone density does decline during blocker treatment, and this is the growth-related concern that clinicians monitor most closely. In one study of 31 transgender girls on blockers for one year, bone density Z-scores at the spine dropped by about 0.44, and at the hip by about 0.5. Transgender boys showed similar or slightly larger declines.
These decreases don’t stop after the first year. Bone density continues to drop as long as suppression lasts, though the rate of decline may slow after the second year. This makes sense biologically: sex hormones play a major role in building bone mass during adolescence, and suppressing them means missing out on some of that critical bone-building window.
Notably, some transgender youth already have lower bone density before starting any treatment. Researchers have pointed to low rates of physical activity as a likely contributor. Weight-bearing exercise, adequate calcium, and vitamin D are consistently recommended during treatment to support bone health. When sex hormones are eventually introduced, bone density typically begins to recover, though long-term data on whether it fully catches up is still being collected.
Why Starting Stage Matters
Puberty blockers are initiated at Tanner stage 2, the earliest physical signs of puberty, such as breast budding or testicular enlargement. Starting at this stage means the adolescent hasn’t yet experienced much of their pubertal growth spurt, so there’s a longer period of slower growth ahead before hormones are introduced. Starting later, at Tanner stage 3 or beyond, means some pubertal growth has already occurred and the remaining window of suppressed growth is shorter.
Clinicians weigh multiple factors when deciding how long to continue blockers: bone age, bone density, height gained so far, and the adolescent’s psychosocial readiness for the next phase of treatment. There’s no single fixed duration. The goal is to balance preserving growth potential and bone health with the adolescent’s overall well-being and treatment timeline.