Congenital GHD results from genetic error, and may be associated with brain structure defects or with midline facial defects such as a cleft palate or single central incisor.

Several genetic defects have been identified:

Growth hormone deficiency IA is autosomal recessive and is characterized by growth retardation in utero. Affected children are small in relation to their siblings. The infant usually has a normal response to administration of human growth hormone (hGH) at first, but then develops antibodies to the hormone and grows into a very short adult.

Growth Hormone Deficiency IB is also autosomal recessive and is similar to IA. However, there is some growth hormone (GH) present in the child at birth and usually the child continues to respond to hGH treatments.

Growth Hormone Deficiency IIB and III are similar to IB, but IIB is autosomal dominant and III is X-linked.

Classic genetic diseases are the product of the interaction of two genes, one received from the father and one from the mother.

Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary to cause a particular disease. The abnormal gene can be inherited from either parent or can be the result of a new mutation (gene change) in the affected individual. The risk of passing the abnormal gene from affected parent to offspring is 50% for each pregnancy. The risk is the same for males and females.

Recessive genetic disorders occur when an individual inherits two copies of an abnormal gene for the same trait, one from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease but usually will not show symptoms. The risk for two carrier parents to both pass the defective gene and have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier like the parents is 50% with each pregnancy.

The chance for a child to receive normal genes from both parents and be genetically normal for that particular trait is 25%. The risk is the same for males and females.

Parents who are close relatives (consanguineous) have a higher chance than unrelated parents to both carry the same abnormal gene, which increases the risk of having children with a recessive genetic disorder.

X-linked genetic disorders are conditions caused by an abnormal gene on the X chromosome and manifest mostly in males. Females that have a defective gene present on one of their X chromosomes are carriers for that disorder. Carrier females usually do not display symptoms because females have two X chromosomes and only one carries the defective gene. Males have one X chromosome that is inherited from their mother and if a male inherits an X chromosome that contains a defective gene he will develop the disease.

Female carriers of an X-linked disorder have a 25% chance with each pregnancy to have a carrier daughter like themselves, a 25% chance to have a non-carrier daughter, a 25% chance to have a son affected with the disease and a 25% chance to have an unaffected son.

If a male with X-linked disorders is able to reproduce, he will pass the defective gene to all of his daughters who will be carriers. A male cannot pass an X-linked gene to his sons because males always pass their Y chromosome instead of their X chromosome to male offspring.

Acquired GHD can occur as a result of many different causes including brain trauma (perinatal or postnatal), central nervous system infection, tumors of the hypothalamus or pituitary (pituitary adenoma, craniopharyngioma, Rathke’s cleft cyst, glioma, germinoma, metastases), radiation therapy, infiltrative diseases (Langerhans cell histiocytosis, sarcoidosis, tuberculosis), or, if without another diagnosis, it is considered idiopathic.