Adrenocorticotropic Hormone (ACTH)

The Adrenocorticotropic Hormone (ACTH) is a tropic hormone, synthesized and secreted by the anterior pituitary gland. It serves a critical function in the body's stress response mechanism. ACTH stimulates the adrenal glands to produce cortisol, colloquially known as the 'stress hormone,' and a variety of androgens, which are sex hormones.

Cortisol, a hormone of paramount importance, influences nearly every organ and tissue in the human body. It performs a multitude of crucial functions, such as modulating the body's stress response, managing the body's metabolism of fats, proteins, and carbohydrates, suppressing inflammation, regulating blood pressure and blood sugar levels, and contributing to the control of the sleep-wake cycle.

In addition to triggering the adrenal glands to release androgens, ACTH also stimulates the production of substances that induce an increase in other hormones, including adrenaline and noradrenaline. The body maintains ACTH levels through a feedback system known as the hypothalamic-pituitary-adrenal (HPA) axis, which involves the hypothalamus, pituitary gland, adrenal glands, and specific hormones.

A deficiency in ACTH is indicative of secondary or tertiary adrenal insufficiency, while persistently elevated ACTH levels are associated with primary adrenal insufficiency, such as Addison's disease. ACTH is not only a critical hormone but also serves as a diagnostic agent and medication in medical practice. The ACTH test, which measures the level of ACTH in the blood, is used to diagnose and monitor conditions that affect cortisol levels, thereby controlling the production of cortisol by the adrenal glands.

Purpose of the Test

• The Adrenocorticotropic hormone (ACTH) test is conducted under various circumstances, including conditions like Adrenal Insufficiency, Acromegaly, and Cushing Syndrome.
• In the case of Addison's Disease, the ACTH level typically exceeds 1000 pg/ml.
• For conditions such as Adrenal Carcinoma, Adenoma, and Adrenocortical Insufficiency, the ACTH level tends to decrease.

Collection of Sample

The estimation of Adrenocorticotropic Hormone (ACTH) requires the patient's plasma. Blood is drawn into a chilled plastic test tube that contains either EDTA or heparin, and it is then placed in cold ice-water. The sample is centrifuged at 4º C, after which the plasma is separated and immediately stored at -20º C within 15 minutes of blood collection.

For diagnosing Cushing Syndrome, the blood sample is collected between 6 PM and 11 PM.

See: Procedures for the collection of blood for hematological investigations

Precautions

1. The blood sample should be collected in a chilled plastic test tube containing either EDTA or heparin.
2. A diet low in carbohydrates should be followed, avoiding high-carb foods.
3. Physical activity should be avoided for 12 hours prior to the collection of the blood sample.
4. Medications such as corticosteroids should be discontinued 48 hours before the blood sample collection.
5. Anxiety during the collection of the blood sample may lead to an increase in the level of Adrenocorticotropic Hormone (ACTH).

Normal Values

• 6 to 8 AM: < 80 pg/ml or < 18 pmol/L (SI units)
• 6 to 11 MP: < 50 pg/ml or < 11 pmol/L (SI units)
  • or less than 120 pg/ml
• According to another references:
  • 8 AM: < 120 pg/mL
  • 4 to 8 PM: < 85 pg/mL
  • Cord blood: 50 to 570 pg/mL
  • Newborn: 10 to 185 pg/mL

Reasons for the increased level of ACTH

1. Cushing syndrome
2. Addison's disease
3. Stress
4. Ectopic ACTH syndrome

Reasons for the decreased level of ACTH

1. Secondary adrenal insufficiency
2. Exogenous steroid administration
3. Hypopituitarism
4. Adrenal adenoma or carcinoma

The significance of Adrenocorticotropic hormone (ACTH) test for the layman

1. This test is recommended in cases of abnormal lipid metabolism.
2. It is advised for patients diagnosed with Diabetes Mellitus (DM).
3. The test is performed for diagnosing Cushing Syndrome.
4. It is recommended when there are symptoms of truncal obesity and thin extremities.