Growth Hormone Deficiency (GHD) and Idiopathic Short Stature (ISS) are the two most common diagnoses that lead to growth hormone therapy in children. Understanding the difference between them helps you make informed decisions about your child's care — and act before the window of opportunity closes.
Growth Hormone Deficiency occurs when the pituitary gland — a small structure at the base of the brain — does not produce enough growth hormone to support normal childhood growth. GHD can be congenital (present from birth) or acquired (developing later due to injury, tumor, or other factors affecting the pituitary).
GHD is confirmed through growth hormone stimulation testing, in which the child receives a medication that should trigger GH release. A peak GH level below 10 ng/mL indicates deficiency. Additional clinical markers typically include:
Children with GHD typically respond excellently to growth hormone therapy. Because the underlying problem is insufficient GH production, replacing what the body isn't making produces rapid and often dramatic improvements in growth velocity — frequently doubling or tripling the pre-treatment growth rate in the first year.
Idiopathic Short Stature is diagnosed when a child's height falls below the 1.2nd percentile (-2.25 standard deviations) with no identifiable medical cause. The word "idiopathic" simply means "of unknown origin." These children produce normal levels of growth hormone on stimulation testing, and no underlying condition — genetic, hormonal, or otherwise — can be found to explain their short stature.
Key characteristics of ISS include:
ISS has been an FDA-approved indication for growth hormone therapy since 2003. While the response may be more moderate than in GHD, treatment still provides meaningful height gains — particularly when started early. Dosing for ISS may be adjusted differently than for GHD, often requiring higher doses to achieve optimal results.
| Factor | GHD | ISS |
|---|---|---|
| Definition | Insufficient GH production by the pituitary gland | Short stature without identifiable cause |
| GH Stimulation Test | Abnormal (peak < 10 ng/mL) | Normal |
| IGF-1 Levels | Often low | Usually normal |
| Bone Age | Typically delayed | May be normal or slightly delayed |
| Growth Velocity | Below normal | Below normal |
| Response to Therapy | Excellent — often dramatic | Good — meaningful but may be more moderate |
| Treatment Duration | 2–5 years | 2–5 years |
| Dosing | Standard protocols | May require higher doses |
Regardless of whether your child is diagnosed with GHD or ISS, one critical fact applies equally to both:
Once growth plates close — which happens permanently in the mid-to-late teenage years — no medication can add inches. Growth hormone therapy can only work while growth plates remain open. Every year of delay reduces the total height gain achievable through treatment. The window is real, finite, and irreversible.
This urgency applies to both GHD and ISS equally. Children who begin treatment at age 6 have far more growth potential remaining than those who start at age 12. If you have concerns about your child's growth, acting sooner always preserves more options.
The cost structure is the same regardless of whether the final diagnosis is GHD or ISS:
Our clinics are cash-pay only — no insurance is accepted or billed. Full cost disclosure is provided before any appointment or commitment.
GHD is diagnosed through growth hormone stimulation testing — if peak GH levels fall below 10 ng/mL, the child is considered growth hormone deficient. ISS is essentially a diagnosis of exclusion: the child's height is below the 1.2nd percentile (-2.25 SD), but GH stimulation testing returns normal results and no other medical cause is found. Both diagnoses also involve bone age X-rays, IGF-1 blood panels, and detailed growth history review.
Our clinics are cash-pay only — we do not accept or bill insurance for any diagnosis. This actually benefits ISS families in particular, because insurance companies frequently deny coverage for ISS treatment even when it is medically appropriate. By operating on a cash-pay model, we eliminate insurance delays and denials entirely, allowing treatment to begin promptly regardless of diagnosis.
Children with GHD typically show the most dramatic response to growth hormone therapy because their bodies were producing insufficient GH to begin with — replacing what's missing produces rapid improvement. Children with ISS also respond meaningfully to therapy, though gains may be more moderate since their bodies already produce normal GH levels. Both groups benefit significantly, and earlier treatment produces better outcomes in both cases.
Not technically, because the two diagnoses are mutually exclusive. GHD means growth hormone production is insufficient, while ISS specifically means GH levels are normal and no medical cause is found. However, some children fall into a gray area — partial GH deficiency — where stimulation test results are borderline. A thorough evaluation by a specialist is the only way to determine the correct diagnosis and optimal treatment approach.
Our care team reviews your child's growth history and helps you understand whether a specialist evaluation may be right for your family. No cost. No obligation. Available nationwide via telemedicine.
Medical Disclaimer: HGHKids.com is a privately operated educational and referral platform. We do not diagnose, treat, or prescribe. All medical decisions are made by licensed physicians following appropriate evaluation. Information on this site is for educational purposes only and does not constitute medical advice.