ACTH

What is ACTH?

ACTH (adrenocorticotropic hormone, also called corticotropin) is a 39-amino-acid peptide secreted by the anterior pituitary gland in response to corticotropin-releasing hormone from the hypothalamus. Its primary job is to act on the adrenal cortex, where it binds the melanocortin-2 receptor (MC2R) and drives the synthesis and release of cortisol and, to a lesser extent, aldosterone and adrenal androgens. Two synthetic forms are used in medicine: cosyntropin (also called tetracosactide or tetracosactrin), a synthetic 24-amino-acid fragment covering the biologically active N-terminus, used almost exclusively as a diagnostic agent; and repository corticotropin injection (Acthar Gel), a long-acting gel formulation of the full 39-residue porcine-derived peptide used therapeutically for a narrow set of inflammatory and neurologic conditions.

What ACTH Is Investigated For

ACTH is one of the most thoroughly characterized peptides in clinical medicine, but almost all of that evidence sits inside a narrow clinical frame rather than the wellness-peptide space. Cosyntropin is the gold-standard diagnostic agent for assessing adrenal reserve — the cosyntropin stimulation test has been the standard of care for primary and secondary adrenal insufficiency for decades. Therapeutically, Acthar Gel (repository corticotropin) is FDA-approved for infantile spasms (where it has strong RCT support), acute MS exacerbations, nephrotic syndrome, and a cluster of rheumatologic indications — though in most of those the modern question is whether Acthar adds anything over high-dose synthetic corticosteroids at a tiny fraction of the cost. ACTH is not used in wellness contexts and is not a plausible self-administered peptide. If you have arrived at this page searching for cortisol support or 'ACTH benefits' in a biohacking sense, the honest framing is that this is a prescription-only hormone used under endocrinologist or subspecialist supervision, not an over-the-counter tool.

History & Discovery

ACTH was isolated in the early 1950s by several groups working on pituitary chemistry, most notably Choh Hao Li at UC Berkeley, who purified the full sequence and characterized its adrenocorticotropic activity. Its therapeutic career began almost immediately after isolation: Philip Hench at the Mayo Clinic had already demonstrated in 1948 that cortisone produced dramatic short-term improvement in rheumatoid arthritis, and ACTH became a natural companion tool, used either to test adrenal function or to drive endogenous cortisol release. The synthetic 1-24 fragment cosyntropin was developed in the 1960s once the active N-terminus was characterized, and it quickly displaced full-length ACTH for diagnostic testing because it was cheaper, less antigenic, and functionally equivalent at MC2R. The repository corticotropin injection (later marketed as Acthar Gel) was introduced as a long-acting injectable to sustain adrenal stimulation over days; it gained FDA approval for a broad list of conditions during the 1950s under a looser regulatory regime than modern NDAs would demand. The drug's subsequent commercial story — low-cost obscurity through the 1990s, then repeated ownership changes and price increases into the 2010s that made a single vial one of the most expensive drugs in US pharmacy benefits — has become a case study in legacy-drug pricing. Clinically, most of its approved indications are now rare or have better-studied alternatives, with infantile spasms the major exception where ACTH remains a standard-of-care first-line therapy.

How It Works

Think of ACTH as the 'go' signal your brain sends to your stress-hormone factory. The pituitary releases it, it travels to the adrenal glands sitting on top of your kidneys, and it tells them to pump out cortisol — the body's main glucocorticoid hormone. Synthetic versions are either used to test whether that factory is working (cosyntropin test) or to deliberately drive it for anti-inflammatory effect (Acthar Gel).

ACTH is cleaved from the larger precursor proopiomelanocortin (POMC) in corticotroph cells of the anterior pituitary. It binds the melanocortin-2 receptor (MC2R), a Gs-coupled receptor expressed predominantly on adrenocortical cells of the zona fasciculata. MC2R activation raises intracellular cAMP, activating protein kinase A, which phosphorylates and activates StAR (steroidogenic acute regulatory protein) to shuttle cholesterol into the mitochondria, the rate-limiting step of steroidogenesis. Downstream, this drives synthesis of cortisol and, in smaller amounts, aldosterone (zona glomerulosa) and adrenal androgens (zona reticularis). Chronic ACTH stimulation causes adrenocortical hyperplasia. Because ACTH shares its first 13 amino acids with alpha-melanocyte-stimulating hormone and has modest affinity for other melanocortin receptors (MC1R, MC3R, MC5R), some of its therapeutic effects in autoimmune disease are hypothesized to include MC1R-mediated anti-inflammatory signaling on leukocytes that is partially independent of the cortisol-mediated pathway — a mechanism cited by advocates of Acthar Gel to explain claimed differences from synthetic glucocorticoids.

Evidence Snapshot

Research Gaps & Open Questions

What the current literature has not yet settled about ACTH:

• 01Whether therapeutic Acthar Gel's claimed melanocortin-receptor-mediated anti-inflammatory effects produce clinically meaningful benefit beyond what equivalent glucocorticoid exposure provides — the central unresolved question for most non-infantile-spasms indications.
• 02Optimal cosyntropin stimulation test cut-offs with modern cortisol immunoassays and LC-MS/MS platforms, where historical thresholds derived from older polyclonal assays may be outdated.
• 03Comparative effectiveness of ACTH versus high-dose oral prednisolone in infantile spasms — both have strong individual RCT support but head-to-head long-term developmental-outcome data remains incomplete.
• 04Long-term developmental and endocrine consequences of early-life high-dose ACTH exposure in treated infantile-spasms cohorts.
• 05Potential role of selective melanocortin receptor agonists (MC1R/MC3R) as successors to repository corticotropin — if the non-glucocorticoid anti-inflammatory mechanism is real, targeted agonists could in principle separate benefit from glucocorticoid toxicity.
• 06Pharmacoeconomic justification for Acthar Gel in indications where inexpensive synthetic glucocorticoids appear therapeutically adequate — an area that has generated litigation more than clinical trials.

Forms & Administration

Cosyntropin (synthetic ACTH 1-24) is administered intravenously or intramuscularly in the 250 mcg standard-dose test, or 1 mcg in the low-dose variant used to detect partial secondary adrenal insufficiency. Acthar Gel is a long-acting intramuscular or subcutaneous depot of full-length porcine corticotropin in a gelatin vehicle, dosed in international units rather than micrograms. ACTH is strictly a prescription medication administered or supervised by a clinician — it is not used in wellness or compounded-peptide contexts.

Dosing & Protocols

The ranges below reflect protocols commonly discussed in the literature and by clinicians — not a prescription. Actual dosing for any individual should be determined by a qualified healthcare provider who knows the patient.

ACTH and cosyntropin are prescription-only medications administered under clinician supervision. Nothing on this page constitutes a suggested self-use protocol. Individuals with known or suspected adrenal insufficiency should be evaluated by an endocrinologist.

Timeline of Effects

Common Questions

Who ACTH Is NOT For

Drug & Supplement Interactions

ACTH's interaction profile follows its downstream glucocorticoid effect much more than any direct receptor-level interaction at MC2R. Because sustained ACTH drives cortisol elevation, clinically relevant interactions overlap substantially with those of systemic corticosteroids. Concurrent NSAIDs increase the risk of GI mucosal injury and bleeding, mirroring the NSAID–glucocorticoid interaction. Potassium-depleting diuretics (loop and thiazide) can compound hypokalemia driven by cortisol's mineralocorticoid activity. Anticoagulants may have altered effect — both potentiation and attenuation are reported with corticosteroid co-administration and are plausible with ACTH. Vaccines: response to live-virus vaccines can be blunted during an active Acthar course, and live vaccination is generally avoided for several weeks following high-dose courses. Insulin and oral antihyperglycemic requirements can rise substantially because cortisol elevation drives hepatic gluconeogenesis and peripheral insulin resistance; diabetic patients on Acthar Gel routinely require glucose monitoring and dose adjustment. Concurrent use with other HPA-axis modulators (high-dose exogenous glucocorticoids, for instance) can complicate adrenal recovery after the course. Antihypertensives may need adjustment because of ACTH-mediated fluid retention. For the single-dose cosyntropin stimulation test, drug interactions are much less of a concern — the main caveats are that exogenous glucocorticoids (including inhaled and topical at high doses) can depress baseline cortisol and confound interpretation, and estrogen-containing contraceptives raise cortisol-binding globulin, which affects measured total cortisol thresholds.

Safety Profile

Legal Status

Regulatory status changes over time. Verify current local rules with a qualified professional.

Myths & Misconceptions