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HESX1 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

HESX1 gene

The HESX1 gene encodes a transcription factor essential for early brain and pituitary gland development, with mutations linked to conditions like septo-optic dysplasia.

Normal Function

The HESX1 gene provides instructions for producing a protein that regulates the activity of other genes. On the basis of this action, the HESX1 protein is called a transcription factor. The HESX1 gene is part of a family of homeobox genes, which act during early embryonic development to control the formation of many body structures.

The HESX1 protein plays an important role in early brain development. In particular, it is essential for the formation of the pituitary, which is a gland at the base of the brain that produces several hormones. The HESX1 protein is also necessary for the development of structures at the front of the brain (the forebrain), including the nerves that carry visual information from the eyes to the brain (optic nerves).

The HESX1 protein interacts with other proteins, including the protein produced from the PROP1 gene, during embryonic development. Both the HESX1 protein and the PROP1 protein bind to DNA and control the activity of other genes. The HESX1 protein turns off (represses) genes, while the PROP1 protein turns on (activates) genes. These proteins work together to coordinate the development of certain parts of the brain.

Health Conditions Related to Genetic Changes

Combined pituitary hormone deficiency

Mutations in the HESX1 gene are associated with combined pituitary hormone deficiency.

Septo-optic dysplasia

At least five mutations in the HESX1 gene have been identified in people with septo-optic dysplasia. Mutations in this gene alter the function of the HESX1 protein, for example by preventing it from binding to DNA and repressing the activity of other genes. HESX1 gene mutations disrupt the formation and early development of the pituitary gland, optic nerves, and other brain structures, leading to the characteristic features of septo-optic dysplasia.

Other disorders

More than a dozen HESX1 gene mutations have been found to cause underdevelopment (hypoplasia) of the pituitary gland in people without the other characteristic features of septo-optic dysplasia. Pituitary hypoplasia leads to a shortage of hormones needed for growth, reproduction, and other critical body functions. Affected individuals may also have:

  • Genital abnormalities
  • Vision impairment
  • Distinctive facial features
  • Extra (supernumerary) fingers

Mutations in the HESX1 gene lead to the production of a defective or nonfunctional HESX1 protein, which disrupts the formation of the pituitary gland during critical stages of embryonic development.

Frequently Asked Questions

Most cases of septo-optic dysplasia associated with HESX1 mutations are autosomal dominant, meaning a single copy of the altered gene is sufficient to cause the condition. However, many cases arise from de novo (new) mutations that were not present in either parent. Because the severity of symptoms can vary widely even within families, genetic counseling is recommended for parents of a child with this condition to understand the recurrence risk for future pregnancies.
The HESX1 protein is essential for the proper development of the pituitary gland. Mutations can lead to combined pituitary hormone deficiency, meaning the gland fails to produce one or more critical hormones. Common deficiencies include growth hormone (leading to short stature), thyroid-stimulating hormone (causing hypothyroidism), and gonadotropins (affecting puberty). In some cases, antidiuretic hormone (ADH) may also be affected, leading to diabetes insipidus, which causes excessive thirst and urination.
Early signs often appear in infancy and may include poor vision or blindness, feeding difficulties due to hormonal imbalances, and developmental delays. Physical examination might reveal a midline brain defect, though this is often confirmed via MRI. Diagnosis typically involves a combination of neurological exams, eye tests, and imaging studies. Blood tests are also crucial to check for pituitary hormone deficiencies, such as low growth hormone or thyroid hormone, which can cause growth failure and hypoglycemia.
With early diagnosis and consistent hormone replacement therapy, many children with HESX1-related conditions can achieve normal growth and development. Regular monitoring by an endocrinologist is vital to adjust hormone doses as the child grows. While visual impairment from optic nerve hypoplasia may be permanent and require special education and vision aids, managing the hormonal aspects effectively can significantly improve quality of life and prevent complications like hypoglycemia or severe growth failure.
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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