congenital disease in which mutations of enzymes that produce steroid hormones result in a glucocorticoid deficiency and malfunction of the negative feedback loop of the HPA axis. In the HPA axis, cortisol (a glucocorticoid) inhibits the release of CRH and ACTH, hormones that in turn stimulate corticosteroid synthesis. As cortisol cannot be synthesized, these hormones are released in high quantities and stimulate production of other adrenal steroids instead. The most common form of congenital adrenal hyperplasia is due to 21-hydroxylase deficiency. 21-hydroxylase is necessary for production of both mineralocorticoids and glucocorticoids, but not androgens. Therefore, ACTH stimulation of the adrenal cortex induces the release of excessive amounts of adrenal androgens, which can lead to the development of ambiguous genitalia and secondary sex characteristics. Adrenal tumors Adrenal tumors are commonly found as incidentalomas, unexpected asymptomatic tumors found during medical imaging. They are seen in around 3.4% of CT scans, and in most cases they are benign adenomas. Adrenal carcinomas are very rare, with an incidence of 1 case per million per year. Pheochromocytomas are tumors of the adrenal medulla that arise from chromaffin cells. They can produce a variety of nonspecific symptoms, which include headaches, sweating, anxiety and palpitations. Common signs include hypertension and tachycardia. Surgery, especially adrenal laparoscopy, is the most common treatment for small pheochromocytomas. History Bartolomeo Eustachi, an Italian anatomist, is credited with the first description of the adrenal glands in 1563–4. However, these publications were part of the papal library and did not receive public attention, which was first received with Caspar Bartholin the Elder's illustrations in 1611. The adrenal glands are named for their location relative to the kidneys. The term "adrenal" comes from Latin ad, "near", and ren, "kidney". Similarly, "suprarenal", as termed by Jean Riolan the Younger in 1629, is derived from the Latin supra, "above", and ren, "kidney", as well. The suprarenal nature of the glands was not truly accepted until the 19th century, as anatomists clarified the ductless nature of the glands and their likely secretory role – prior to this, there was some debate as to whether the glands were indeed suprarenal or part of the kidney. One of the most recognized works on the adrenal glands came in 1855 with the publication of On the Constitutional and Local Effects of Disease of the Suprarenal Capsule, by the English physician Thomas Addison. In his monography, Addison described what the French physician