Cosyntropin

At a glance

Overview

Cortrosyn contains the first twenty-four amino acids of ACTH, which retain the adrenal-stimulating activity needed for a diagnostic challenge. Clinicians measure cortisol responses in conjunction with other information when investigating possible adrenal insufficiency. A result must be interpreted with the assay, timing, illness context and the suspected location of a hormonal defect in mind. The current label specifically addresses misleading cortisol values from medicines and altered cortisol-binding globulin. A single stimulated total-cortisol measurement therefore should not be treated as a complete explanation for chronic tiredness or every suspected endocrine disorder.

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How it works

Cosyntropin activates ACTH receptors on adrenal cortical cells and stimulates steroid synthesis, including cortisol. Measuring the resulting cortisol response tests the adrenal gland’s capacity to respond to that stimulus. It does not directly measure every aspect of hypothalamic or pituitary function. Total cortisol is also affected by binding proteins, so a change in measured concentration can reflect more than adrenal steroid production alone.

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Approved diagnostic role

The current U.S. label authorizes use with other diagnostic tests to screen for adrenocortical insufficiency in adults and children. It does not authorize general hormone enhancement or ongoing adrenal replacement.

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Why assay and context matter

The response is one component of an endocrine assessment. Laboratory methods and clinical circumstances influence the threshold used to judge adequacy, while the distinction between primary adrenal disease and central causes may require additional information.

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Medicines can distort the result

Glucocorticoids, spironolactone and estrogen-containing drugs can affect cortisol measurement or cortisol-binding globulin. The label provides test-preparation considerations, which should be managed by the testing clinician rather than through unsupervised medication changes.

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Adverse reactions and protein binding

Hypersensitivity, including anaphylaxis, has been reported and is an important immediate risk. Cirrhosis, nephrotic syndrome and other states altering cortisol-binding globulin can produce misleading total cortisol levels without a corresponding change in biologically active hormone.

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Why it differs from corticotropin therapy

Cosyntropin is a short synthetic fragment used as a diagnostic stimulus. Repository corticotropin is used therapeutically for selected diseases. Sharing ACTH activity does not make the products interchangeable or transfer their indications and long-term safety assumptions.

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