Clinical and genetic analysis of primary bilateral adrenal diseases (micro-and macronodular disease) leading to Cushing syndrome

Primary bilateral adrenocortical diseases are rare entities that have recently been appreciated as potential causes of Cushing syndrome. They include (i) primary pigmented adrenocortical disease (PPNAD), also known as "micronodular adrenal disease", which is a genetic disorder that is often associated with Carney complex, and (ii) massive macronodular adrenocortical disease (MMAD), a rare disorder of unknown etiology that affects older adults. Carney complex is a multiple endocrine neoplasia (MEN) syndrome that affects not only the adrenal cortex, but also the pituitary, thyroid, and gonads. It is associated with pigmentation abnormalities as well as myxomas and other mesenchymal and neural crest neoplasms. The inheritance of the complex is autosomal dominant, and genetic mapping has shown that at least two loci are involved in its pathogenesis. MMAD appears to be an isolated finding in most cases, and a genetic defect has not yet been defined. Ectopic expression of hormone receptors has been implicated in several cases of MMAD, but an underlying deficit has not been detected. Bilateral adrenocortical hyperplasia has also been described in McCune-Albright syndrome and MEN type-1, but this finding is not always associated with hypercortisolism. The genetic defects for these diseases are known, but their role in adrenal cortex pathophysiology has not been fully elucidated. Identification of the molecular defects responsible for bilateral adrenocortical disorders is expected to shed light on many aspects of early adrenal gland differentiation and tumorigenesis.