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GNAS gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

GNAS gene

The GNAS gene is a complex locus that regulates hormone production and bone development, with mutations leading to a variety of endocrine and skeletal disorders.

Normal Function

The GNAS gene provides instructions for the stimulatory alpha subunit of a G protein. This protein complex regulates the activity of an enzyme called adenylate cyclase, which controls the production of hormones in endocrine glands, including the thyroid, pituitary, ovaries, testes, and adrenal glands. Adenylate cyclase also plays a key role in bone development (osteogenesis) by preventing the formation of bone tissue in inappropriate locations.

Health Conditions Related to Genetic Changes

McCune-Albright syndrome

Somatic mutations in the GNAS gene cause McCune-Albright syndrome. These mutations lead to constitutive activation of adenylate cyclase, resulting in the overproduction of hormones. Because the mutation occurs early in development, individuals exhibit mosaicism, where only some cells carry the mutated gene.

Primary macronodular adrenal hyperplasia (PMAH)

Mutations in the GNAS gene can lead to PMAH, characterized by nodules in the adrenal glands and the overproduction of cortisol. This can cause weight gain, fragile skin, bone loss, and fatigue.

Progressive osseous heteroplasia

This condition is caused by mutations affecting the paternal copy of the GNAS gene. Due to genomic imprinting, the disruption of this gene impairs the regulation of osteogenesis, leading to the ectopic production of bone tissue in skin and muscles.

Albright hereditary osteodystrophy (AHO)

Mutations in the GNAS gene cause AHO, which presents with short stature, obesity, and skeletal abnormalities. The clinical presentation depends on the parent of origin:

  • Maternally inherited: AHO accompanied by hormone resistance (pseudohypoparathyroidism type Ia).
  • Paternally inherited: AHO without endocrine problems (pseudopseudohypoparathyroidism).

Frequently Asked Questions

Early signs of PMAH often mimic other forms of Cushing syndrome and include gradual weight gain, particularly in the trunk and face, along with the development of purple stretch marks and thin, fragile skin that bruises easily. Patients may also experience significant fatigue, muscle weakness, and high blood pressure. Because the adrenal glands produce excess cortisol, individuals might also notice mood changes, sleep disturbances, or irregular menstrual cycles in women, which should prompt a referral for endocrine testing.
Management of POH focuses on preventing the progression of ectopic bone formation in the skin and muscles. Patients are advised to avoid trauma or repetitive stress to affected areas, as injury can trigger further ossification. Regular physical therapy is essential to maintain joint mobility and muscle strength, while orthopedic monitoring is required to address skeletal deformities. Pain management and, in severe cases, surgical intervention to remove excess bone tissue may be necessary to preserve function.
The clinical severity of AHO depends on whether the GNAS mutation is inherited from the mother or the father due to genomic imprinting. When inherited from the mother, the condition presents with both the physical features of AHO (short stature, round face, brachydactyly) and hormone resistance, specifically pseudohypoparathyroidism type 1a, which affects calcium and phosphate regulation. When inherited from the father, patients typically exhibit the physical features of AHO but do not develop the endocrine hormone resistance, resulting in a milder clinical course regarding metabolic function.
McCune-Albright syndrome is caused by somatic mutations, meaning the genetic change occurs after conception in specific cells rather than being inherited from a parent. Because of this, it is not passed down through families, and the mutation is often not detectable in standard blood tests. Diagnosis typically relies on identifying the characteristic triad of symptoms: café-au-lait skin spots, fibrous dysplasia of the bones, and endocrine hyperfunction, such as precocious puberty or thyroid overactivity.
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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