Anterior Pituitary

Overview

What is the anterior pituitary?

The anterior pituitary is the front lobe of your pituitary gland, which is a small, pea-sized gland located at the base of your brain below your hypothalamus. Your pituitary gland is a part of your endocrine system and controls the function of several other endocrine glands.

Your pituitary gland is made of two lobes: the anterior (front) lobe and posterior (back) lobe. The anterior pituitary creates and releases over six different hormones, which regulate various cellular processes including:

  • Growth.
  • Metabolism (how your body transforms and manages energy from the food you eat).
  • Reproduction.
  • Response to stress or trauma.
  • Lactation.

What is the pituitary gland?

Your pituitary gland is a small gland located at the base of your brain below your hypothalamus. It’s in charge of making many different important hormones. Your pituitary gland also tells other endocrine system glands to release hormones.

Your pituitary gland is connected to your hypothalamus through a stalk of blood vessels and nerves. This is called the pituitary stalk. Through the stalk, your hypothalamus communicates with your pituitary gland and tells it to release certain hormones. Your hypothalamus is the part of your brain that controls functions like blood pressure, heart rate, body temperature and digestion.

Your pituitary gland makes the following hormones:

  • Adrenocorticotropic hormone (ACTH or corticotropin).
  • Antidiuretic hormone (ADH, or vasopressin).
  • Follicle-stimulating hormone (FSH).
  • Growth hormone (GH).
  • Luteinizing hormone (LH).
  • Oxytocin.
  • Prolactin.
  • Thyroid-stimulating hormone (TSH).

Your pituitary gland doesn’t produce and release all of these hormones continuously. Most are released in bursts every one to three hours, alternating between periods of activity and inactivity.

Another term to describe the release of hormones from your pituitary gland is pulsatile. Your pituitary gland may secrete some hormones based on your circadian rhythm.

What is the endocrine system?

Your endocrine system is a network of several glands that create and secrete (release) hormones.

A gland is an organ that makes one or more substances, such as hormones, digestive juices, sweat or tears. Endocrine glands release hormones directly into your bloodstream.

Hormones are chemicals that coordinate different functions in your body by carrying messages through your blood to your organs, muscles and other tissues. These signals tell your body what to do and when to do it.

The following organs and glands make up your endocrine system:

  • Hypothalamus.
  • Pituitary gland.
  • Thyroid.
  • Parathyroid glands.
  • Adrenal glands.
  • Pineal gland.
  • Pancreas.
  • Ovaries.
  • Testes.

Function

What hormones are secreted by the anterior pituitary?

Your anterior pituitary produces and releases (secretes) six main hormones:

  • Adrenocorticotropic hormone (ACTH, or corticotropin): This hormone stimulates your adrenal glands (the glands on top of your kidneys) to produce cortisol and other hormones.
  • Follicle-stimulating hormone (FSH): This hormone stimulates the testes to produce sperm and stimulates the ovaries to produce eggs and estrogen.
  • Luteinizing hormone (LH): This hormone stimulates ovulation in women and testosterone production in men.
  • Growth hormone (GH): In children, growth hormone stimulates growth. In adults, growth hormone helps maintain healthy muscles and bones and impacts fat distribution.
  • Prolactin: This hormone stimulates breast milk production after giving birth and can affect menstrual periods, fertility and sexual function (by causing low testosterone in people assigned male at birth and low estrogen in people assigned female at birth).
  • Thyroid-stimulating hormone (TSH): This hormone stimulates your thyroid to produce hormones that manage metabolism, energy and your nervous system.

How does the anterior pituitary interact with other organs and glands?

Your anterior pituitary interacts directly with your hypothalamus since your hypothalamus regulates it by secreting the “releasing hormones" somatostatin and dopamine through blood vessels in the pituitary stalk. These releasing hormones either stimulate or inhibit (prevent) the creation and release of anterior pituitary hormones. Your hypothalamus and anterior pituitary are in constant communication with each other.

The anterior pituitary hormones interact with and affect several different organs, glands and tissues in your body, including:

  • Bones, muscles and organs — growth hormone (GH).
  • Adrenal gland — adrenocorticotropic hormone (ACTH).
  • Thyroid gland — thyroid-stimulating hormone (TSH).
  • Ovaries and testes — luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
  • Mammary glands — prolactin.

Anatomy

Where is the anterior pituitary located?

Your pituitary gland is located at the base of your brain, behind the bridge of your nose and directly below your hypothalamus. It sits in a small chamber or pouch in the sphenoid bone called the sella turcica.

Your pituitary gland is made of two lobes that touch each other. The anterior pituitary is in the front and is facing the front of your head, whereas the posterior pituitary is the back lobe of your pituitary gland, meaning it is facing the back of your head.

How big is the anterior pituitary?

Your pituitary gland is only about 1/3 of an inch in diameter in total — about the size of a pea. The anterior pituitary is bigger than the posterior pituitary and accounts for about 80% of the total weight of your pituitary gland.

What is the anterior pituitary made of?

The anterior pituitary is made of cell clusters that produce six hormones and release them into your bloodstream. Different types of cell clusters create and release different hormones, including:

  • Corticotrophs produce adrenocorticotrophic hormone (ACTH).
  • Thyrotrophs produce thyroid-stimulating hormone (TSH).
  • Somatotrophs produce growth hormone (GH).
  • Gonadotrophs produce follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
  • Lactotrophs produce prolactin (PRL).

Conditions and Disorders

Several different conditions are related to issues with the anterior pituitary since it produces so many different hormones. In general, the majority of conditions related to the anterior pituitary are due to hypopituitarism (underactive pituitary gland) or hyperpituitarism (overactive pituitary gland). In these conditions, your anterior pituitary either produces too little or too much of one or more hormones.

Hypopituitarism and hyperpituitarism are generally caused by one of the following conditions or situations:

  • Pituitary gland tumors (adenomas).
  • Damage to your anterior pituitary, hypothalamus or pituitary stalk through injury, infection or blood loss.
  • Genetic conditions, such as multiple endocrine neoplasia (MEN).

Hypopituitarism conditions

Conditions that are the result of lower-than-normal levels of one or more anterior pituitary hormones include:

  • Secondary adrenal insufficiency: Usually, adrenocorticotrophic hormone (ACTH) signals your adrenal glands to make cortisol, an essential hormone. If your pituitary gland produces low levels of ACTH, it leads to an underactive adrenal gland. This is known as central or secondary adrenal insufficiency (not to be confused with Addison’s disease, which is cortisol deficiency due to a primary adrenal gland problem).
  • Growth hormone deficiency: This condition happens when your anterior pituitary releases lower-than-normal levels of growth hormone (GH). A deficiency in GH in adults can cause changes in body composition due to changes in fat and muscle, unhealthy cholesterol levels and loss of energy. If GH deficiency in children leads to poor overall growth and short height.
  • Hypogonadism (low sex hormones): Hypogonadism occurs when sex glands don’t produce enough sex hormones, which can affect your sex drive and fertility. It can happen when your anterior pituitary releases lower-than-normal levels of follicle-stimulating hormone (FSH) and/or luteinizing hormone (LH), leading in turn to low levels of testosterone and estrogen.
  • Hypothyroidism: If your anterior pituitary releases too little thyroid-stimulating hormone (TSH), it can cause hypothyroidism, which is when your thyroid gland is underactive and releases too little of its own hormones.

Hyperpituitarism conditions

Conditions that are the result of higher-than-normal levels of one or more anterior pituitary hormones include:

  • Acromegaly: Acromegaly is a very rare condition that happens when a benign (noncancerous) tumor in your anterior pituitary produces too much growth hormone (GH). It affects your body’s bones and tissues and causes them to grow in abnormal ways. Acromegaly affects adults, and common symptoms include an increase in size of your hands, feet, lips and jaw.
  • Cushing’s disease: Cushing’s syndrome happens when your adrenal glands make too much cortisol. Cushing’s disease, a type of Cushing’s syndrome, happens when your adrenal glands are making too much cortisol because of a problem in your anterior pituitary. Cushing’s disease is caused by a benign tumor in your anterior pituitary that makes excess adrenocorticotrophic hormone (ACTH), which causes your adrenal glands to make too much cortisol. It can cause rapid weight gain, mainly in your face, abdomen and the back of your neck, as well as other symptoms.
  • Hyperthyroidism: If your anterior pituitary releases too much thyroid-stimulating hormone (TSH), usually from a benign pituitary tumor, it can cause hyperthyroidism, which is when your thyroid gland is overactive and releases too much of its own hormones. This is a very rare cause of hyperthyroidism.

Pituitary gland tumors (adenomas)

A pituitary adenoma is a growth or tumor on your pituitary gland. Most pituitary adenomas are slow-growing and benign (noncancerous). Adenomas can put pressure on normal pituitary cells and keep them from working properly, leading to hypopituitarism, especially when they are large. They can also release extra pituitary hormones, leading to hyperpituitarism (pituitary hormone excess).

Pituitary adenomas make up 10% to 15% of all tumors that develop within the skull. They are found in about 77 out of 100,000 people, although researchers believe that they actually occur in as many as 20% of people at some point in their lives. However, many pituitary adenomas, especially very small ones, don’t cause serious symptoms and are never discovered.

What tests can check the health of my anterior pituitary?

If you’re experiencing symptoms related to anterior pituitary issues, your healthcare provider may order tests to check one or more of your anterior pituitary hormone levels, depending on what your symptoms are. These tests are usually blood tests.

If your test results come back abnormal, your provider may suggest undergoing an imaging test such as an MRI (magnetic resonance imaging) to take a look at your pituitary gland.

A note from Cleveland Clinic

Since your anterior pituitary is responsible for several different hormones that affect many aspects of your body and health, it can be difficult to pinpoint if certain symptoms are a result of issues with your anterior pituitary. If you’re ever experiencing new or concerning symptoms, it’s important to talk to your healthcare provider. They can usually run some simple tests to assess your health.

Last reviewed by a Cleveland Clinic medical professional on 12/21/2021.

References

  • Merck Manual Consumer Version. Hypopituitarism. (https://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/pituitary-gland-disorders/hypopituitarism) Accessed 12/21/2021.
  • Merck Manual Consumer Version. Overview of the Pituitary Gland. (https://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/pituitary-gland-disorders/overview-of-the-pituitary-gland#v27731602) Accessed 12/21/2021.
  • Rawindraraj AD, Basit H, Jialal I. Physiology, Anterior Pituitary. (https://www.ncbi.nlm.nih.gov/books/NBK499898/) In: StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing; 2021. Accessed 12/21/2021.

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