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Isolated growth hormone deficiency
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

Isolated growth hormone deficiency

Isolated growth hormone deficiency is a condition characterized by a severe shortage or absence of growth hormone, leading to slow growth and short stature.

Overview

Isolated growth hormone deficiency is a condition caused by a severe shortage or absence of growth hormone, a protein necessary for the normal growth of the body's bones and tissues. People with this condition commonly experience a failure to grow at the expected rate and have unusually short stature, which is usually apparent by early childhood.

Types

There are four types of isolated growth hormone deficiency, differentiated by the severity of the condition, the gene involved, and the inheritance pattern:

  • Type IA: The most severe form, caused by an absence of growth hormone. Growth failure is evident in infancy, as affected babies are shorter than normal at birth.
  • Type IB: Characterized by very low levels of growth hormone. Growth failure is typically not as severe as in type IA and is usually apparent in early to mid-childhood.
  • Type II: Individuals have very low levels of growth hormone and short stature of varying severity. Nearly half of these individuals have underdevelopment of the pituitary gland (pituitary hypoplasia).
  • Type III: Similar to type II, individuals have very low levels of growth hormone and short stature. Affected people may also have a weakened immune system and are prone to frequent infections due to a lack of specialized B cells (agammaglobulinemia).

Causes

Isolated growth hormone deficiency is caused by mutations in at least three genes:

  • GH1 gene: Provides instructions for making the growth hormone protein. Mutations prevent or impair the production of growth hormone, leading to types IA, IB, and II.
  • GHRHR gene: Provides instructions for the growth hormone-releasing hormone receptor. Mutations impair the production or release of growth hormone, responsible for many cases of type IB.
  • BTK gene: Provides instructions for the Bruton tyrosine kinase protein, essential for the development of immune system cells called B cells. Mutations in this gene cause type III.

When no genetic cause is identified, the condition is known as idiopathic isolated growth hormone deficiency.

Inheritance

  • Types IA and IB: Inherited in an autosomal recessive pattern, meaning both copies of the GH1 or GHRHR gene in each cell have mutations.
  • Type II: Inherited in an autosomal dominant pattern, where a mutation in one copy of the GH1 gene is sufficient to cause the disorder. It can also result from de novo mutations.
  • Type III: Inherited in an X-linked recessive pattern. Because males have only one X chromosome, they are affected more frequently than females.

Frequently Asked Questions

Type IA, caused by a complete absence of the growth hormone protein due to GH1 gene mutations, generally does not respond to standard recombinant human growth hormone (rhGH) injections because the body cannot produce the hormone at all. In contrast, Type II involves very low levels of GH but not a complete absence, so these patients typically respond well to daily rhGH injections, which can restore normal growth velocity and adult height. Treatment plans are tailored based on the specific genetic mutation and the residual function of the pituitary gland.
Yes, the condition is inherited in an autosomal recessive pattern. This means both parents must carry one copy of the mutated gene to have an affected child. If a couple has one child with isolated GH deficiency, there is a 25 percent chance with each subsequent pregnancy that the child will also be affected. Genetic counseling is recommended for parents to understand the inheritance risks and to discuss options for prenatal or preimplantation genetic testing.
Diagnosis often relies on monitoring growth velocity and performing stimulation tests. Since Type IA presents with short stature at birth, clinicians may measure insulin-like growth factor 1 (IGF-1) levels early. For Types IB, II, and III, where growth failure becomes apparent later, doctors typically administer a growth hormone stimulation test using agents like arginine or clonidine to see if the pituitary gland can release adequate GH. Genetic testing for mutations in the GH1, AIP, or GHRHR genes can confirm the specific type and rule out other pituitary disorders.
Type III is unique because it is associated with agammaglobulinemia, a condition where the body lacks specialized B cells responsible for producing antibodies. This leads to a weakened immune system and a high susceptibility to frequent, severe bacterial infections. While other types primarily affect growth and stature, patients with Type III require not only growth hormone therapy but also immunoglobulin replacement therapy to prevent life-threatening infections.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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