Adrenocorticotrophic hormone, also known as corticotrophin or simply ACTH, is produced by the pituitary and its function is to stimulate the production of steroid hormones by the adrenal cortex (adrenal and pituitary glands), such as cortisol, aldosterone and androgens.
Thus, ACTH measurement is important to investigate alterations related to the pituitary and adrenal glands, such as Cushing’s syndrome, Addison’s disease, adrenal gland insufficiency or hypopituitarism, for example.
The ACTH test is usually ordered along with cortisol measurements to assess the relationship between these two hormones, as ACTH stimulates cortisol production. It is recommended that the test be performed in the morning, as the level of ACHT varies throughout the day, with greater concentration being verified in the morning.
When is the ACTH test indicated
The ACTH test is usually indicated by the physician when there is suspicion of abnormalities in the adrenal or pituitary gland or when the person has signs or symptoms that are indicative of excessive or deficient cortisol production, such as:
- Signs and symptoms of increased cortisol production: overweight, thin and fragile skin, reddened stretch marks on the belly, acne, increased body hair;
- Signs and symptoms of deficient cortisol production: weakness, tiredness, weight loss, skin darkening and loss of appetite.
This test is usually ordered along with cortisol dosage, since ACTH stimulates cortisol production. Thus, by evaluating the levels of these two hormones together, it is possible to reach a diagnosis. Depending on the diagnosis, imaging exams may also be requested, especially when tumors are suspected.
How is done
The ACTH test is done based on the evaluation of a blood sample, which should preferably be collected in the morning, since it is during this period that the highest ACTH concentration is normally verified. This hormone is secreted gradually during the day, having higher levels at 6 and 8 am and lower levels at 9 pm and 10 pm.
To perform this exam it is not necessary to fast or any other preparation, being the main recommendation to perform the exam in the morning. In addition, it is recommended that the use of supplements containing biotin be discontinued for at least 3 days before the exam or as directed by the physician.
what does the result mean
ACTH levels can be influenced by the time of day, as the levels vary greatly throughout the day, and by everyday situations such as stress and anxiety, for example. In general, the normal value of ACTH in the blood between 7 and 10 am should be between 7 and 63 pg/mL. It is important to keep in mind that the reference value may vary depending on the laboratory and analysis method used.
ACTH high
High ACHT, which is when a concentration above 63 pg/mL is verified between 7 am and 10 am, may be indicative of some situations, the main ones:
- Cushing’s syndrome, which can lead to increased production of ACTH by the pituitary;
- Primary adrenal insufficiency;
- Adrenogenital syndrome with decreased cortisol production;
- Use of amphetamines, insulin, levodopa, metoclopramide and mifepristone.
Very high concentrations of ACTH in the blood can increase the breakdown of lipids, increasing the concentration of fatty acids and glycerol in the blood, stimulate the secretion of insulin and increase the production of the growth hormone, GH.
ACTH low
Low ACHT, which is when a concentration below 7 pg/mL is verified between 7 and 10 am, may be indicative of some situations, such as hypopituitarism, pituitary insufficiency of ACTH (secondary adrenal) or be a consequence of the use of some medications, such as corticosteroids, estrogens, spironolactone, amphetamines, alcohol, lithium, pregnancy, menstrual cycle phase, physical activity.
