What is Adrenocorticotropic Hormone Definition Secretion and Functions
Hormones are steroidal substances that are secreted from different organs. These biochemical substances are developed to control and manage various biological functions. Most human hormones are secreted by the pituitary gland present in the lower portion of the human brain. It is also called the master gland that controls the functions of other organs. One such hormone produced by the pituitary gland is adrenocorticotropic hormone (ACTH). In this section, we will study the ACTH function elaborately and the disorders caused by its abnormal levels.
What is ACTH Hormone?
Adrenocorticotropic Hormone (ACTH) is a steroidal substance that acts as a hormone. It is produced in the anterior section of the pituitary gland located under the human brain. This hormone is commonly called adrenocorticotrophin, arginine vasopressin, corticotropin, or serum adrenocorticotropic hormone.
This hormone is required for the functioning of the adrenal glands. As you can easily understand by its name, the prime ACTH hormone function is to maintain the vital functions of this pair of glands. These glands are responsible for the production and secretion of cortisol or stress hormones. These hormones are produced in the cortex region of these glands.
How ACTH is Synthesized?
The first stage is the production and release of the Corticotrophin-releasing hormone. This hormone acts as the precursor of the synthesis and release of ACTH. ACTH, after synthesis and release, reaches the bloodstream to reach the adrenal glands. These glands are present on the top of both kidneys. The cortisols are then synthesized in the cortex of these glands. These hormones then reach the hypothalamus of our brain to signal and stop the synthesis of ACTH.
Now that we have understood the answer for what is ACTH hormone, we need to go deeper into the synthesis and control of the ACTH level in our body. It is obvious that the hormone travels through the bloodstream and reaches the adrenal glands for action. It has been observed that the level of this hormone is the highest when you wake up in the morning. Eventually, it reduces throughout the day and is the lowest before you go to sleep. The level is controlled but three crucial organs of our body. They are the hypothalamus, adrenal glands, and pituitary gland.
We have learned that the level of this hormone is controlled by the cortisol or stress hormones present in the bloodstream. We also know that the lowest level of ACTH occurs during the night time when we are about to hit the bed. This proves that working relentlessly and taking stress release cortisol in the bloodstream. These stress hormones then reach the hypothalamus telling it to shut down the production. The ACTH hormone levels then significantly fall over the day in due course of time and action. This rhythmic synthesis and reduction of the ACTH hormone level during the daytime are called the diurnal or circadian rhythm.
Functions of ACTH Hormone
The list of ACTH functions is given below:
Resorption of bones
Protein catabolism
Anabolic effects of this hormone can be seen on bones and muscles
Proper stimulation and beginning of spermatogenesis
Proper metabolism of glucose, lipolysis, hyperglycemia, androgens, and immuno-suppression.
What Happens When the ACTH Level Drops?
When the ACTH hormone levels drop significantly, it can cause anomalies that are related to the functioning of the adrenal glands. It can happen due to hypopituitarism or the low functioning of the master gland. Cushing’s syndrome can also increase the level of cortisol that affects the synthesis of ACTH causing such issues.
What Happens When the ACTH Hormone Levels Increase?
The ATH level can significantly increase due to hyperpituitarism, Cushing’s disease, adrenal insufficiency (low cortisol levels), adrenal hyperplasia in the congenital condition, etc. Due to the increased ACTH level, it can cause Addison’s disease.
What are the ACTH Hormone Disorders?
When there is an improper level of ACTH in the bloodstream, it can indicate the presence of an anomaly in the physiology of the brain, the adrenal glands, etc. It can happen due to tumours present in the pituitary gland, Cushing’s disease, adrenal insufficiencies such as Addison’s disease, or congenital adrenal hyperplasia.
Conclusion
The definition of this hormone depicts the ACTH hormone function that is crucial for the proper functioning and development of the human body. It indicates the adrenal glands develop and promotes their functions. Indirectly, the functions of the adrenal glands are controlled by this hormone. The hormones produced in these glands are aldosterone, cortisol, noradrenaline, and adrenaline. These hormones function to control metabolism, blood sugar levels, water-slat balance, blood pressure, pregnancy, puberty, sexual characteristics development, balancing the sex hormones, etc.
FAQs on Adrenocorticotropic Hormone ACTH in the Endocrine System
1. What is Adrenocorticotropic Hormone (ACTH)?
Adrenocorticotropic Hormone (ACTH) is a tropic peptide hormone produced by the anterior pituitary gland that stimulates the adrenal cortex to release cortisol.
- ACTH is also called corticotropin.
- It acts mainly on the adrenal cortex.
- Its primary target hormone is cortisol, a key stress hormone.
- It is an essential part of the endocrine system and hormonal regulation.
2. What is the function of ACTH in the body?
The main function of ACTH is to stimulate the adrenal cortex to produce and release cortisol.
- Promotes synthesis of glucocorticoids, especially cortisol.
- Helps regulate the body’s stress response.
- Supports metabolism of carbohydrates, proteins, and fats.
- Maintains normal blood pressure and immune responses.
3. How does ACTH stimulate cortisol release?
ACTH stimulates cortisol release by binding to receptors on cells of the adrenal cortex, activating intracellular signaling that promotes cortisol synthesis.
- ACTH binds to melanocortin 2 receptors (MC2R).
- Activates the cAMP signaling pathway.
- Stimulates conversion of cholesterol into cortisol.
- Cortisol is then released into the bloodstream.
4. Where is ACTH produced?
ACTH is produced and secreted by the anterior lobe of the pituitary gland in the brain.
- Specifically secreted by corticotroph cells.
- Its release is stimulated by corticotropin-releasing hormone (CRH) from the hypothalamus.
- It is part of the hypothalamic–pituitary–adrenal (HPA) axis.
5. What is the HPA axis and how is ACTH involved?
The hypothalamic–pituitary–adrenal (HPA) axis is a hormonal feedback system that controls stress responses, and ACTH is the central pituitary hormone in this pathway.
- The hypothalamus releases CRH.
- CRH stimulates the anterior pituitary to release ACTH.
- ACTH stimulates the adrenal cortex to release cortisol.
- Cortisol exerts negative feedback on both hypothalamus and pituitary.
6. What happens when ACTH levels are too high?
Excess ACTH leads to overproduction of cortisol, a condition commonly associated with Cushing’s disease.
- Usually caused by a pituitary adenoma.
- Results in high cortisol levels.
- Symptoms include weight gain, high blood pressure, and muscle weakness.
- May also cause skin pigmentation due to ACTH’s similarity to melanocyte-stimulating hormone (MSH).
7. What happens when ACTH levels are too low?
Low ACTH levels result in decreased cortisol production, leading to secondary adrenal insufficiency.
- Caused by pituitary dysfunction.
- Leads to low cortisol levels.
- Symptoms include fatigue, weakness, and low blood pressure.
- Different from Addison’s disease, where the adrenal gland itself is damaged.
8. How is ACTH secretion regulated?
ACTH secretion is regulated by a negative feedback mechanism involving CRH and cortisol in the HPA axis.
- CRH from the hypothalamus stimulates ACTH release.
- ACTH stimulates cortisol secretion.
- High cortisol levels inhibit CRH and ACTH production.
- Stress, infection, and trauma increase ACTH secretion.
9. What is the difference between ACTH and cortisol?
ACTH is a pituitary hormone that stimulates the adrenal gland, while cortisol is a steroid hormone produced by the adrenal cortex in response to ACTH.
- ACTH: Peptide hormone from anterior pituitary.
- Cortisol: Steroid hormone from adrenal cortex.
- ACTH controls cortisol release.
- Cortisol affects metabolism, immunity, and stress response.
10. Why is ACTH important in the stress response?
ACTH is important in the stress response because it triggers cortisol release, which helps the body cope with physical and emotional stress.
- Increases blood glucose availability.
- Enhances energy metabolism.
- Suppresses non-essential processes like certain immune functions.
- Prepares the body for a fight-or-flight response.
