Constitutional Growth Delay vs. Familial Short Stature: What Parents Should Know
Both patterns produce a shorter-than-average boy, but the growth arc, timing, and eventual adult height are very different. Here is how pediatricians tell them apart.
The two patterns in one paragraph
Constitutional growth delay (CGD) is late blooming. The boy tracks a low line, grows normally for his age, starts puberty later than peers, and reaches a normal adult height on a delayed timeline. About 2% of boys.
Familial short stature (FSS) is genetic shortness. The boy tracks a low line, grows normally for his age, hits puberty on a normal timeline, and reaches an adult height that matches his family (shorter parents produce a shorter son). Not a diagnosis, just genetics playing out.
Side-by-side comparison
| Feature | Constitutional delay (CGD) | Familial short stature (FSS) |
|---|---|---|
| Growth pattern | Low percentile, normal velocity | Low percentile, normal velocity |
| Puberty timing | Late (starts 14+) | On time (10-14) |
| Bone age | Delayed vs. chronological | Matches chronological |
| Family history | Late-blooming dad or uncle common | Short parents typical |
| Adult height | Normal, reached 1-2 years later | Below average, matching family |
| Treatment | Usually none; optional short-course testosterone | Usually none; genetics not treatable |
How pediatricians tell them apart
- Family height. Short parents plus a short son on-track for mid-parental target usually = FSS. Average parents plus a short son with delayed timing = often CGD.
- Bone age x-ray. The single most useful test. Delayed bone age is the hallmark of CGD; matched bone age is the hallmark of FSS.
- Puberty stage. A 14-year-old with no signs of puberty and delayed bone age is likely CGD. A 14-year-old fully in puberty who is just short is likely FSS.
What treatment looks like for each
CGD: Usually no treatment needed. Wait, and adult height arrives on a delayed timeline. Optional: short-course low-dose testosterone (3-6 months) to kick-start the spurt earlier. Does not change final height, only timing.
FSS: Growth hormone therapy is FDA-approved for boys more than 2.25 standard deviations below the mean (idiopathic short stature). Gains are modest (1-2 inches over years of treatment) and expensive. Whether it makes sense is a family conversation with pediatric endocrinology.
The middle ground: a boy with both
Many boys have some of both. Short-ish family plus later-than-typical puberty. In these cases, the adult height ends up somewhat below the mid-parental midpoint but usually higher than the low end of the family range.
When to ask for a workup
- Height below the 3rd percentile.
- Percentile crossing lines downward.
- Growth velocity below age ranges.
- No signs of puberty by age 14.
- Any concern the current pattern does not match family history.
Height data uses the CDC 2000 Growth Charts for boys. This page is parent education, not medical advice or diagnosis. If you have concerns about your son's growth, talk to his pediatrician, ideally with 6-12 months of measurements in hand. © 2026 The Growth Path.