ACTH 1-39 (Corticotropin)

ACTH 1-39 is the full-length, biologically active form of adrenocorticotropic hormone, a 39-amino-acid peptide synthesized in the anterior pituitary as a cleavage product of proopiomelanocortin (POMC). Its primary physiological role is to stimulate the adrenal cortex to produce and release cortisol — the cornerstone of the hypothalamic-pituitary-adrenal (HPA) stress axis. ACTH binds the melanocortin-2 receptor (MC2R) on adrenocortical cells with high specificity. It also binds, at lower affinity, the other melanocortin receptors (MC1R-MC5R), accounting for secondary effects including skin pigmentation changes with prolonged use.

In clinical medicine, ACTH itself has been replaced for most diagnostic uses by the synthetic shorter fragment cosyntropin (ACTH 1-24, Cortrosyn). Repository ACTH gel (Acthar Gel, full-length porcine ACTH in long-acting formulation) remains FDA-approved for a range of inflammatory and rheumatologic conditions including infantile spasms, multiple sclerosis exacerbations, and certain forms of nephrotic syndrome — though its clinical use is controversial because of high cost and limited evidence beyond the historical approvals.

Research uses of ACTH 1-39 span endocrinology (HPA axis studies), neuroscience (the ACTH 4-10 fragment is the parent of Semax and related nootropic peptides), and dermatology (melanocortin-receptor research). It is not a wellness or lifestyle peptide — it produces large cortisol surges with all the metabolic, immunological, and mood consequences of pharmacologic hypercortisolism. It is included in this category here because of its mechanistic connection to the ACTH-derived cognitive peptides (Semax, Adamax) but it does not have the same use case.

ACTH was isolated and sequenced in the 1950s by Choh Hao Li at UC Berkeley, who shared in the broader work on pituitary hormones recognized by the 1971 Nobel Prize. Synthetic ACTH 1-39 became available in the 1960s and was used both as a diagnostic agent and as an anti-inflammatory therapy. The shorter cosyntropin fragment replaced full-length ACTH for diagnostic use in most countries by the 1980s. Repository ACTH gel (Acthar) was approved by the FDA in 1952 for an extremely broad set of indications, most of which have not been re-evaluated under modern evidence standards.