What Is the Posterior Pituitary and What Does It Do?

The posterior pituitary is the smaller of two lobes that make up your pituitary gland. It secretes vasopressin and oxytocin into your bloodstream — hormones that play a role in water balance, childbirth, and sexual activity, among others.

The posterior pituitary is part of your pituitary gland, located at the base of your brain. It stores and releases two hormones: vasopressin and oxytocin. These play an important role in regulating various bodily functions.

In this article, we take a closer look at the location and function of the posterior pituitary. We also go over the conditions that can affect this organ.

The posterior pituitary is located at the base of your brain, attached to the hypothalamus. It’s one of the two lobes that together form your pituitary gland. The front lobe is called the anterior pituitary, while the back lobe is called the posterior pituitary.

How big is the posterior pituitary?

The pituitary gland is roughly the size and shape of a kidney bean, one-third of an inch in diameter. It weighs around 1 gram (0.03 ounces). The posterior pituitary is smaller than the anterior pituitary. Despite its tiny size, the posterior pituitary plays a crucial role in controlling various bodily functions.

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The posterior pituitary is responsible for storing and releasing the hormones vasopressin and oxytocin into your bloodstream.

Production of these hormones takes place in your hypothalamus. The hypothalamus is connected to your pituitary gland through a stalk-like structure that contains nerve cells and blood vessels.

Your hypothalamus sends vasopressin and oxytocin to the posterior pituitary through the blood vessels in the stalk. It also uses it to tell the posterior pituitary when they need to be released into your bloodstream.

Share on Pinterest Illustration by Alexis Lira

The posterior pituitary stores and releases two hormones: vasopressin and oxytocin.

Vasopressin

Vasopressin is also known as the antidiuretic hormone (ADH). ADH helps regulate your body’s water balance by making your kidneys conserve more water. It also helps maintain blood pressure by constricting (or narrowing) blood vessels in your body.

Oxytocin

Oxytocin stimulates the contractions of a birthing parent’s uterus during childbirth. It also promotes breast milk production after the baby is born. Oxytocin release during feeding boosts bonding between the parent and the baby.

Oxytocin is known as the “love hormone.” In addition to the parent-baby bonding, it’s responsible for many human behaviors and social interactions, for example:

  • sexual arousal and ejaculation
  • recognition
  • trust
  • romantic attachment
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Disorders of the posterior pituitary affect its ability to store and release hormones. They’re most often caused by noncancerous tumors called pituitary adenomas.

Generally, posterior pituitary disorders need treatment if they make your pituitary gland release too much hormone or not enough of it. If a pituitary adenoma doesn’t affect your hormone levels, it rarely causes any symptoms and usually doesn’t require treatment.

Let’s go over a few conditions that can affect your posterior pituitary.

Diabetes insipidus

Low levels of ADH can cause diabetes insipidus. It makes your kidneys unable to conserve enough water. The main symptoms of this condition are excessive thirst and increased urine output.

Diabetes insipidus affects around 1 in 25,000 people .

Syndrome of inappropriate antidiuretic hormone secretion (SIADH)

SIADH, on the other hand, is due to too much ADH in your blood. It’s more common in older people and those in hospitals.

This condition makes it difficult for your body to get rid of excess water. This causes a buildup of fluids and low blood sodium levels. Symptoms are often mild at first but tend to build. They include:

  • irritability
  • headaches
  • loss of appetite
  • nausea and vomiting
  • muscle cramps
  • difficulty concentrating
  • confusion

Oxytocin issues

Hyposecretion, or lack of oxytocin, isn’t common. It can affect a person’s uterine contractions and milk production during and after childbirth.

Hypersecretion, or too much oxytocin, is very rare. It’s called oxytocin toxicity. It can cause an increase in uterine muscle mass, which can affect the development of a baby in the womb.

The treatment for posterior pituitary disorders depends on the specific condition and its severity. Mild forms of posterior pituitary conditions often don’t require treatment.

If the gland is not secreting enough of a hormone, a doctor may consider hormone replacement therapy. For example, diabetes insipidus can be treated with desmopressin, a synthetic form of ADH.

If the gland is secreting too much of a hormone, treatment may involve medications that counteract the hormone’s function. For example, doctors can treat SIADH with medications that reduce fluid retention.

The posterior pituitary is the back lobe of your pituitary gland. It’s a part of your brain responsible for storing and releasing two hormones, vasopressin (ADH) and oxytocin.

ADH regulates your water balance by telling your kidney to conserve more water. Diabetes insipidus and SIADH are examples of posterior pituitary disorders that affect the secretion of this hormone.

Oxytocin is involved in controlling childbirth, nursing, parent-child bonding, and romantic bonding. Disorders affecting this hormone aren’t common.

Treatment of posterior pituitary disorders depends on the specific condition but may involve hormone replacement therapy and other medications.

Last medically reviewed on April 11, 2023

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