05/12/2015 11:30 PM EDT
Source: National Library of Medicine
Related MedlinePlus Page: Adrenal Gland Disorders
Related MedlinePlus Page: Adrenal Gland Disorders
Primary macronodular adrenal hyperplasia
What is PMAH?
Primary macronodular adrenal hyperplasia (PMAH) is a disorder characterized by multiple lumps (nodules) in the adrenal glands, which are small hormone-producing glands located on top of each kidney. These nodules, which usually are found in both adrenal glands (bilateral) and vary in size, cause adrenal gland enlargement (hyperplasia) and result in the production of higher-than-normal levels of the hormone cortisol. Cortisol is an important hormone that suppresses inflammation and protects the body from physical stress such as infection or trauma through several mechanisms including raising blood sugar levels.
PMAH typically becomes evident in a person's forties or fifties. It is considered a form of Cushing syndrome, which is characterized by increased levels of cortisol resulting from one of many possible causes. These increased cortisol levels lead to weight gain in the face and upper body, fragile skin, bone loss, fatigue, and other health problems. However, some people with PMAH do not experience these signs and symptoms and are said to have subclinical Cushing syndrome.
How common is PMAH?
PMAH is a rare disorder. It is present in less than 1 percent of cases of endogenous Cushing syndrome, which describes forms of Cushing syndrome caused by factors internal to the body rather than by external factors such as long-term use of certain medicines called corticosteroids. The prevalence of endogenous Cushing syndrome is about 1 in 26,000 people.
What genes are related to PMAH?
In about half of individuals with PMAH, the condition is caused by mutations in the ARMC5 gene. This gene provides instructions for making a protein that is thought to act as a tumor suppressor, which means that it helps to prevent cells from growing and dividing too rapidly or in an uncontrolled way. ARMC5 gene mutations are believed to impair the protein's tumor-suppressor function, which allows the overgrowth of certain cells. It is unclear why this overgrowth is limited to the formation of adrenal gland nodules in people with PMAH.
PMAH can also be caused by mutations in the GNAS gene. This gene provides instructions for making one component, the stimulatory alpha subunit, of a protein complex called a guanine nucleotide-binding protein (G protein). The G protein produced from the GNAS gene helps stimulate the activity of an enzyme called adenylate cyclase. This enzyme is involved in controlling the production of several hormones that help regulate the activity of certain endocrine glands, including the adrenal glands. The GNAS gene mutations that cause PMAH are believed to result in an overactive G protein. Research suggests that the overactive G protein may increase levels of adenylate cyclase and result in the overproduction of another compound called cyclic AMP (cAMP). An excess of cAMP may trigger abnormal cell growth and lead to the adrenal nodules characteristic of PMAH.
Mutations in other genes, some of which are unknown, can also cause PMAH.
See a list of genes associated with PMAH.
How do people inherit PMAH?
People with PMAH caused by ARMC5 gene mutations inherit one copy of the mutated gene in each cell. The inheritance is considered autosomal dominant because one copy of the mutated gene is sufficient to make an individual susceptible to PMAH. However, the condition develops only when affected individuals acquire another mutation in the other copy of the ARMC5 gene in certain cells of the adrenal glands. This second mutation is described as somatic. Instead of being passed from parent to child, somatic mutations are acquired during a person's lifetime and are present only in certain cells. Because somatic mutations are also required for PMAH to occur, some people who have inherited the altered ARMC5 gene never develop the condition, a situation known as reduced penetrance.
When PMAH is caused by GNAS gene mutations, the condition is not inherited. The GNAS gene mutations that cause PMAH are somatic mutations. In PMAH, the gene mutation is believed to occur early in embryonic development. Cells with the mutated GNAS gene can be found in both adrenal glands.
Where can I find information about diagnosis or management of PMAH?
These resources address the diagnosis or management of PMAH and may include treatment providers.
- Eunice Kennedy Shriver National Institute of Child Health and Human Development: How Do Health Care Providers Diagnose Adrenal Gland
- Eunice Kennedy Shriver National Institute of Child Health and Human Development: What are the Treatments for Adrenal Gland
- Genetic Testing Registry: Acth-independent macronodular adrenal hyperplasia
You might also find information on the diagnosis or management of PMAH in Educational resourcesand Patient support.
General information about the diagnosis and management of genetic conditions is available in the Handbook. Read more about genetic testing, particularly the difference between clinical tests and research tests.
To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.
Where can I find additional information about PMAH?
You may find the following resources about PMAH helpful. These materials are written for the general public.
You may also be interested in these resources, which are designed for healthcare professionals and researchers.
What other names do people use for PMAH?
- ACTH-independent macronodular adrenal hyperplasia
- ACTH-independent macronodular adrenocortical hyperplasia
- adrenal Cushing syndrome due to AIMAH
- adrenocorticotropic hormone-independent macronodular adrenal hyperplasia
- corticotropin-independent macronodular adrenal hyperplasia
- primary bilateral macronodular adrenal hyperplasia
What if I still have specific questions about PMAH?
Where can I find general information about genetic conditions?
The Handbook provides basic information about genetics in clear language.
- What does it mean if a disorder seems to run in my family?
- What are the different ways in which a genetic condition can be inherited?
- If a genetic disorder runs in my family, what are the chances that my children will have the condition?
- Why are some genetic conditions more common in particular ethnic groups?
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding PMAH?
adrenal glands ; autosomal ; autosomal dominant ; bilateral ; bone loss ; cell ; compound ;embryonic ; enzyme ; gene ; guanine ; hormone ; hyperplasia ; infection ; inflammation ; inherit ;inheritance ; inherited ; kidney ; mutation ; nucleotide ; penetrance ; prevalence ; protein ; stress ;subunit ; syndrome ; trauma ; tumor
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (7 links)
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook