# Short Stature Evaluation and Growth Hormone Therapy

## Introduction

Short stature is one of the most common reasons for referral to pediatric endocrinology. It is defined as height below the 3rd percentile (or less than -2 standard deviations) for age and sex, or a growth velocity below the 25th percentile sustained over 6-12 months. While most children with short stature have normal variants (familial short stature or constitutional delay), a systematic evaluation is essential to identify pathological causes that require intervention.

## Normal Growth Patterns

During infancy (0-2 years), growth is rapid but decelerating, with 25 cm gained in the first year and 12 cm in the second year. Infants may cross percentiles as they shift from intrauterine growth influences to genetic potential. During childhood (2 years to puberty), growth is steady at 5-7 cm per year, and the growth channel is usually established by age 2-3. During puberty, growth accelerates to 8-12 cm per year in girls and 10-14 cm per year in boys. Girls peak earlier (Tanner II-III) than boys (Tanner III-IV).

Mid-parental height (MPH) estimates the genetic target: for boys, it is calculated as (mother's height + father's height + 13 cm) / 2, and for girls, as (mother's height + father's height - 13 cm) / 2, with a target range of MPH plus or minus 8.5 cm.

## Differential Diagnosis

### Normal Variants

Familial short stature (FSS) features short parents, normal growth velocity, normal bone age, and a predicted adult height consistent with mid-parental height. Constitutional delay of growth and puberty (CDGP) features delayed bone age, delayed puberty, a family history of late bloomers, and a normal but time-shifted growth velocity. Adult height is typically normal.

### Pathological Causes

Endocrine causes include growth hormone deficiency (GHD), hypothyroidism, Cushing syndrome, precocious puberty (early fusion), and poorly controlled diabetes. Genetic and syndromic causes include Turner syndrome (45,X), Noonan syndrome, Prader-Willi syndrome, Russell-Silver syndrome, SHOX gene deficiency, and skeletal dysplasias (achondroplasia). Chronic disease causes include celiac disease, inflammatory bowel disease, chronic kidney disease, cystic fibrosis, congenital heart disease, and chronic infections. Nutritional causes include caloric deprivation, malabsorption, and eating disorders. Psychosocial short stature (deprivation dwarfism) is reversible with an improved environment. Iatrogenic causes include chronic glucocorticoid therapy, stimulant medications, and radiation to the spine or hypothalamus.

### Proportionate vs Disproportionate Short Stature

Proportionate short stature is seen in most endocrine, nutritional, and systemic causes. Disproportionate short stature (abnormal upper-to-lower segment ratio or arm span-to-height ratio) suggests skeletal dysplasias, rickets, or mucopolysaccharidoses.

<image>Growth chart illustration showing characteristic growth patterns for familial short stature (parallel to but below normal curves, normal bone age), constitutional delay (delayed bone age, late pubertal growth spurt, catch-up to normal adult height), and growth hormone deficiency (progressive falling away from growth curve)</image>

## Evaluation

### History

The history should include birth weight and length (SGA vs AGA), perinatal complications, growth velocity trend (the single most important parameter), parental heights and pubertal timing, nutritional intake, chronic illness symptoms, medications, psychosocial environment, and developmental milestones.

### Physical Examination

Accurate height, weight, head circumference, and growth velocity calculation are essential. Body proportions (sitting height, arm span, upper/lower segment ratio) should be assessed. Dysmorphic features such as midline defects, webbed neck, shield chest, cubitus valgus, and micropenis should be noted. Tanner staging may reveal delayed puberty explaining the short stature. Fundoscopic examination assesses for optic nerve hypoplasia (septo-optic dysplasia) or papilledema (craniopharyngioma).

### Laboratory and Imaging

First-line labs include CBC, CMP, ESR/CRP, celiac panel (tTG-IgA plus total IgA), TSH, free T4, IGF-1, and IGFBP-3. Bone age (left hand and wrist X-ray) is delayed in CDGP, GHD, and hypothyroidism, and advanced in precocious puberty and CAH. Karyotype should be obtained in all girls with unexplained short stature because Turner syndrome may have a subtle phenotype. GH stimulation testing is performed if IGF-1 is low and clinical suspicion for GHD exists. Two provocative tests are required (arginine, clonidine, glucagon, insulin tolerance test), and a GH peak less than 10 ng/mL on two tests suggests GHD (the cutoff varies by assay). Brain MRI with pituitary protocol is obtained if GHD is confirmed, assessing for pituitary hypoplasia, ectopic posterior pituitary, empty sella, midline defects, or tumors.

<image>Diagnostic algorithm for short stature evaluation starting with growth velocity assessment, branching into normal velocity (familial short stature, constitutional delay) versus decreased velocity pathways with endocrine, genetic, systemic, and nutritional workup steps</image>

## Growth Hormone Therapy

### FDA-Approved Indications in Children

| FDA-Approved Indication | Key Criteria |
|------------------------|-------------|
| Growth hormone deficiency | GH peak <10 ng/mL on two stimulation tests |
| Turner syndrome (45,X) | Confirmed karyotype |
| Chronic kidney disease | Pre-transplant growth failure |
| Prader-Willi syndrome | Genetic confirmation |
| Small for gestational age | No catch-up by age 2-4 years |
| Idiopathic short stature | Height < -2.25 SD |
| SHOX gene deficiency | Genetic confirmation |
| Noonan syndrome | Clinical/genetic diagnosis |

Approved indications include growth hormone deficiency (the most common indication), Turner syndrome, chronic kidney disease (pre-transplant), Prader-Willi syndrome, small for gestational age (SGA) without catch-up growth by age 2-4 years, idiopathic short stature (height less than -2.25 SD), SHOX gene deficiency, and Noonan syndrome.

### Administration and Dosing

Recombinant human GH (rhGH) is given as a subcutaneous injection, typically daily at bedtime to mimic physiologic nocturnal GH secretion. The dose varies by indication from 0.024-0.067 mg/kg/day, with the highest doses used for Turner syndrome and SGA. Long-acting GH preparations requiring only weekly injection are increasingly available, such as somapacitan and lonapegsomatropin.

### Monitoring

Growth velocity should improve to 8-12 cm per year in the first year of treatment, with response diminishing over time. IGF-1 levels should be kept in the upper-normal range while avoiding supraphysiologic levels. Bone age is assessed annually to determine remaining growth potential. Fasting glucose and HbA1c should be monitored because GH is diabetogenic and can cause insulin resistance. Thyroid function should be monitored because GH can unmask or worsen central hypothyroidism. Scoliosis surveillance is particularly important in Turner syndrome and Prader-Willi syndrome.

### Side Effects and Safety

GH therapy is generally well tolerated. Common side effects include injection site reactions, arthralgias, and edema. Rare but serious complications include intracranial hypertension (pseudotumor cerebri) and slipped capital femoral epiphysis (SCFE), as well as worsening of scoliosis. Contraindications include active malignancy, proliferative diabetic retinopathy, closed epiphyses, and Prader-Willi syndrome with severe obesity or respiratory compromise.

<image>Illustration showing proper GH injection technique with subcutaneous injection sites marked on a child's body, alongside a graph demonstrating expected first-year growth response to GH therapy compared to pretreatment growth velocity</image>

## Clinical Pearls

Growth velocity is more important than a single height measurement: a child on the 5th percentile growing at a normal velocity is reassuring, while a child crossing percentiles downward is concerning. Every girl with unexplained short stature needs a karyotype because Turner syndrome can present without classic phenotypic features. IGF-1 is a screening tool, not a definitive test; a normal IGF-1 does not exclude GHD, and a low IGF-1 can reflect malnutrition. Thyroid function and celiac serologies should always be checked before attributing short stature to GHD, as these are common and treatable causes. Psychosocial short stature resolves dramatically with environmental change and does not require GH therapy.

## References
1. Grimberg A, DiVall SA, Polychronakos C, et al. Guidelines for Growth Hormone and Insulin-Like Growth Factor-I Treatment in Children and Adolescents: Growth Hormone Deficiency, Idiopathic Short Stature, and Primary Insulin-Like Growth Factor-I Deficiency. *Horm Res Paediatr*. 2016;86(6):361-397.
2. Cohen P, Rogol AD, Deal CL, et al. Consensus Statement on the Diagnosis and Treatment of Children with Idiopathic Short Stature. *J Clin Endocrinol Metab*. 2008;93(11):4210-4217.
3. Collett-Solberg PF, Ambler G, Backeljauw PF, et al. Diagnosis, Genetics, and Therapy of Short Stature in Children: A Growth Hormone Research Society International Perspective. *Horm Res Paediatr*. 2019;92(1):1-14.
4. Allen DB, Cuttler L. Short Stature in Childhood — Challenges and Choices. *N Engl J Med*. 2013;368(13):1220-1228.