ACTH Test - An Overview

Introduction

The ACTH test is a blood test that gauges the levels of ACTH (adrenocorticotropic hormone), a hormone produced by the pituitary gland located at the base of the brain. This hormone prompts the adrenal glands situated on top of the kidneys to produce cortisol, a crucial hormone that regulates blood pressure, responds to infections, and breaks down sugar, fat, and protein in food. It is essential to note that the ACTH test is distinct from the ACTH stimulation test. In case the physician suspects that the adrenal or pituitary glands are producing excess or insufficient cortisol or ACTH, they may recommend an ACTH test. Additionally, ACTH goes by other names, such as serum adrenocorticotropic hormone, highly-sensitive ACTH, adrenocorticotrophin, and corticotropin.

What Is Adrenocorticotropic Hormone?

The release of cortisol and androgens in response to stress is primarily regulated by a hormone called adrenocorticotropic hormone (ACTH). This hormone is produced and released by the anterior pituitary gland, a pea-sized gland located at the base of the brain, as a part of the body's endocrine system. Hormones like ACTH carry messages through the bloodstream to various organs and tissues, coordinating different functions and telling the body what to do and when to do it.

What Is the Purpose of ACTH Test?

Usually, a cortisol test is performed alongside an ACTH test, as the symptoms of excessive or insufficient ACTH primarily stem from excessive or deficient cortisol levels. The following are symptoms associated with excess ACTH causing an overproduction of cortisol:

• Weight gain.

• Accumulation of fat in the shoulders.

• Pink or purple marks on certain body parts.

• Increased vulnerability to bruising.

• The greater amount of body hair.

• Muscle weakness.

• Fatigue.

• Acne.

• Hyperpigmentation.

The symptoms associated with insufficient cortisol levels are:

• Weight loss.

• Nausea or vomiting.

• Diarrhea.

• Abdominal discomfort.

• Dizziness.

• Dark spots on the skin.

• Craving for salt.

• Fatigue.

Assessing the levels of ACTH in the bloodstream can aid the physician in detecting various other medical conditions, including:

• Cushing's syndrome (a condition with excess cortisol hormone causing weight gain and health issues).

• Cushing's disease (caused by a pituitary tumor, leading to excessive cortisol and health issues).

• Addison's disease (a rare condition where the adrenal glands do not produce enough hormones, causing fatigue, weakness, and other health problems).

• Tumor growth outside the pituitary gland.

• Inadequate hormone production by the pituitary and adrenal glands.

How to Get Prepared for ACTH Test?

In the case of steroids, patients may need to discontinue using them for up to 48 hours before the test to prevent their interference with the test results. Moreover, the physician may advise limiting the carbohydrate intake for 48 hours before the test. Additionally:

• Refrain from eating or drinking anything after midnight.

• Ensure to have adequate sleep the night before the test.

• Avoid engaging in physical activity within 12 hours leading up to the test.

• Evade any emotional stress 12 hours before the test.

• Inform the physician about any prescribed or non-prescribed medication, dietary supplements, vitamins, herbal remedies, or recreational drugs.

How to Perform ACTH Test?

Typically, an initial test measuring the cortisol and ACTH levels is conducted early in the morning, and a medical professional may schedule the test for the earliest possible time. Afterward, the patient will typically receive an intramuscular injection of cosyntropin, a synthetic form of ACTH that typically induces cortisol production.

Around 30 and/or 60 minutes following the injection, a healthcare provider will draw a blood sample by inserting a needle into a vein, usually located inside the elbow, to test cortisol levels. The doctor may caution against the use of any steroid medications, including corticosteroids, before the test, as they may alter the accuracy of the results.

What Do the ACTH Test Results Mean?

The usual range for baseline ACTH values is between 10 and 60 picograms per milliliter (pg/mL), though this range may differ slightly across laboratories. Any level outside of this range may indicate specific health conditions. During an ACTH stimulation test, medical professionals measure cortisol levels in response to stress. If the cortisol levels fail to increase or increase inadequately after receiving the cosyntropin injection in comparison to the baseline levels, it might be an indication of adrenal insufficiency. A doctor may require further tests to confirm a diagnosis based on the results. Possible diagnoses include:

• Addison's Disease: It happens when the adrenal cortex is damaged, and the adrenal glands cannot produce enough cortisol and aldosterone hormones.

• Hypopituitarism: It occurs when the pituitary gland does not make enough of some or all of its hormones.

• Congenital Adrenal Hyperplasia: It is a birth defect that causes the adrenal glands to produce cortisol and aldosterone at atypical rates.

• Adrenoleukodystrophy: It refers to rare conditions that affect the nervous system and adrenal glands, including Addison's disease.

• Nelson's Syndrome: This rare condition occurs when an ACTH-producing tumor in the pituitary gland after the surgical removal of both adrenal glands due to Cushing's disease.

What Is the Follow-up Process for an ACTH test?

The diagnosis of a condition affecting the production of ACTH or cortisol can be complex, requiring additional laboratory tests and physical examination by a doctor. If excessive cortisol production is caused by an ACTH-secreting tumor, medical treatment and surgery may be necessary. Surgery is usually recommended for tumors causing a high ACTH level, while medication can be an alternative for those not fit for surgery. In the case of hypercortisolism due to adrenal tumors, surgery is typically required. A high ACTH level may also indicate a condition like Addison’s disease, where hormone production is insufficient, and hormone replacement medication is often prescribed. Anti-inflammatory medication may also be necessary.

Is There Any Risk Associated With the ACTH Test?

There is a small risk of bleeding, infection, or fainting associated with the blood draw during an ACTH test. However, these risks are generally low and rare. In rare cases, the cosyntropin injection can cause an allergic reaction. It is important to inform the healthcare provider about any known allergies or history of severe allergic reactions. Overall, the risk associated with an ACTH test is generally considered to be minimal.

Conclusion

The ACTH test measures ACTH levels in the blood to detect medical conditions such as Cushing's syndrome, Addison's disease, and hormone production issues. It involves measuring cortisol and ACTH levels in the morning, injecting synthetic ACTH, and re-measuring cortisol levels. Abnormal ACTH levels may require further testing and examination by a doctor.