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Healthy subjects rarely have antibodies against other endocrine glands, but this is common in patients with autoimmune adrenal insufficiency. Over half of patients with autoimmune adrenal insufficiency have high serum antithyroid peroxidase antibody concentrations; nearly half of these patients have overt hypothyroidism. Many others have subclinical hypothyroidism (increased thyroid-stimulating hormone with normal serum thyroxine concentrations); these patients are at risk for developing overt hypothyroidism (Schmidt syndrome). [ 6 ]
1. Cortisol secretion. Cortisol secretion is regulated mainly by ACTH. ACTH is a 39-amino acid peptide that is produced in the anterior pituitary. It is synthesized as part of a larger mol wt precursor peptide, POMC. This peptide is also the source of β -lipotropin (β-LPH). In addition, ACTH and β-LPH are cleaved further to yield α-MSH and β-MSH, γ-LPH, β- and γ-endorphin, and enkephalin. The POMC precursor peptide is found in a variety of extrahypothalamic tissues, including the gastrointestinal tract, numerous tumors, and the testis. It is secreted in small amounts from the anterior pituitary gland and does not bind significantly to the ACTH receptor. Another pro-ACTH fragment, corticotropin-like intermediate lobe peptide (CLIP), is made in the rodent anterior pituitary, but not in the normal human pituitary ( 18 ).