GHR Gene

Laron syndrome is a rare form of short stature that results from the body's inability to use growth hormone, a substance produced by the brain's pituitary gland that helps promote growth. Affected individuals are close to normal size at birth, but they experience slow growth from early childhood that results in very short stature. If the condition is not treated, adult males typically reach a maximum height of about 4.5 feet; adult females may be just over 4 feet tall.

Other features of untreated Laron syndrome include reduced muscle strength and endurance, low blood sugar levels (hypoglycemia) in infancy, small genitals and delayed puberty, hair that is thin and fragile, and dental abnormalities. Many affected individuals have a distinctive facial appearance, including a protruding forehead, a sunken bridge of the nose (saddle nose), and a blue tint to the whites of the eyes (blue sclerae). Affected individuals have short limbs compared to the size of their torso, as well as small hands and feet. Adults with this condition tend to develop obesity. However, the signs and symptoms of Laron syndrome vary, even among affected members of the same family.

Studies suggest that people with Laron syndrome have a significantly reduced risk of cancer and type 2 diabetes. Affected individuals appear to develop these common diseases much less frequently than their unaffected relatives, despite having obesity (a risk factor for both cancer and type 2 diabetes). However, people with Laron syndrome do not seem to have an increased lifespan compared with their unaffected relatives.

Familial hypercholesterolemia is an inherited condition characterized by very high levels of cholesterol in the blood. Cholesterol is a waxy, fat-like substance that is produced in the body and obtained from foods that come from animals (particularly egg yolks, meat, poultry, fish, and dairy products). The body needs this substance to build cell membranes, make certain hormones, and produce compounds that aid in fat digestion. In people with familial hypercholesterolemia, the body is unable to get rid of extra cholesterol, and it builds up in the blood. Too much cholesterol increases a person's risk of developing heart disease.

People with familial hypercholesterolemia have a high risk of developing a form of heart disease called coronary artery disease at a young age. This condition occurs when excess cholesterol in the bloodstream is deposited on the inner walls of blood vessels, particularly the arteries that supply blood to the heart (coronary arteries). The abnormal buildup of cholesterol forms clumps (plaques) that narrow and harden artery walls. As the plaques get bigger, they can clog the arteries and restrict the flow of blood to the heart. The buildup of plaques in coronary arteries causes a form of chest pain called angina and greatly increases a person's risk of having a heart attack.

Familial hypercholesterolemia can also cause health problems related to the buildup of excess cholesterol in tissues other than the heart and blood vessels. If cholesterol accumulates in the tissues that attach muscles to bones (tendons), it causes characteristic growths called tendon xanthomas. These growths most often affect the Achilles tendons, which attach the calf muscles to the heels, and tendons in the hands and fingers. Yellowish cholesterol deposits can develop under the skin of the eyelids and are known as xanthelasmata. Cholesterol can also accumulate at the edges of the clear, front surface of the eye (the cornea), leading to a gray-colored ring called an arcus cornealis.