Idiopathic short stature (ISS) describes a condition where a child’s height falls significantly below average for their age and sex, with no identifiable medical reason for this reduced growth. This diagnosis means extensive medical evaluations have not found an underlying disease or genetic syndrome. Growth hormone (GH), a naturally occurring substance, plays a fundamental role in regulating a child’s height development. Its ability to promote growth makes it a treatment consideration for ISS.
Understanding Idiopathic Short Stature
The term “idiopathic” indicates the cause of short stature remains unknown, distinguishing it from other forms of growth delay. A diagnosis of short stature applies when a child’s height falls below the 3rd or 5th percentile on standard growth charts for their age and sex. This means only three to five out of 100 children would be shorter.
For an ISS diagnosis, healthcare professionals must first rule out all other medical explanations. These include nutritional deficiencies (e.g., severe malnutrition, celiac disease), chronic diseases (e.g., kidney disease, heart conditions, asthma), genetic syndromes (e.g., Turner, Noonan), and endocrine disorders (e.g., hypothyroidism, growth hormone deficiency). Comprehensive diagnostic testing is used to exclude these conditions.
The Role of Growth Hormone
Growth hormone (GH) is a polypeptide hormone produced by the anterior pituitary gland, a small gland at the base of the brain. It is a primary regulator of linear growth in children, stimulating growth plates at the ends of long bones. GH promotes the proliferation and differentiation of chondrocytes, forming new bone tissue and increasing bone length.
GH also influences metabolism, promoting protein synthesis, mobilizing fats for energy, and affecting glucose metabolism. While children with ISS produce detectable GH levels, their bodies may not produce enough or utilize it effectively to achieve a typical height. Administering exogenous growth hormone can stimulate growth plates, potentially helping these children achieve a greater adult height.
Determining the Need for Treatment
The diagnostic process for idiopathic short stature involves a thorough evaluation to exclude other medical conditions. This begins with a detailed medical history and physical examination, followed by specialized tests. Blood tests assess thyroid function, kidney and liver health, and markers for celiac disease. Levels of insulin-like growth factor 1 (IGF-1) and IGF-binding protein 3 (IGFBP-3), which are stimulated by growth hormone, are also measured.
A bone age X-ray, typically of the left wrist and hand, assesses skeletal maturity, indicating if bone development is significantly delayed. Genetic tests, such as a karyotype for chromosomal abnormalities like Turner syndrome, or specific gene panels, may be considered if clinically warranted.
Criteria for considering growth hormone treatment for ISS include a height below 2.25 standard deviations below the mean for age and sex (approximately the 1.2th percentile) and a low growth velocity (less than 4 to 5 centimeters per year after age two or three). The decision-making process is a collaborative effort between pediatric endocrinologists, the child, and their family. Factors considered include the child’s current height, predicted adult height, and the potential psychological impact of short stature. The objective of treatment is to improve adult height potential and mitigate psychosocial challenges.
Navigating Growth Hormone Treatment
Growth hormone for idiopathic short stature is administered as a daily subcutaneous injection. Parents or caregivers are trained to give these injections at home, often in the evening to mimic the body’s natural nocturnal GH release. Treatment continues until the child reaches their final adult height or until their growth plates have fused, usually in late adolescence.
Families can expect a gradual increase in growth velocity, with an initial growth spurt in the first year, followed by a more consistent rate. Overall height gain varies, with studies showing an average increase of 4 to 7 centimeters (approximately 1.6 to 2.8 inches) compared to untreated individuals with ISS.
Potential side effects are generally mild and uncommon, including headaches, mild joint or muscle pain, or temporary fluid retention, which often resolve with dosage adjustments. More serious side effects, such as slipped capital femoral epiphysis (a hip problem) or idiopathic intracranial hypertension (increased pressure around the brain), are rare but require immediate medical attention. Ongoing medical supervision involves regular check-ups every 3 to 6 months to monitor growth progress, assess for side effects, and adjust dosage based on weight changes and IGF-1 levels.