Posterior Pituitary: Hormones, Functions, Conditions and Care
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer: What is the posterior pituitary?
The posterior pituitary is the back lobe of the pituitary gland. Its main job is to store and release ADH and oxytocin, hormones produced by the hypothalamus. ADH helps control kidney water reabsorption, while oxytocin affects several reproductive and bonding-related functions. [1]
Core idea | Plain-language meaning |
Location | At the base of the brain, below the hypothalamus. |
Part of | The pituitary gland and endocrine system. |
Lobe | The back, or posterior, lobe. |
Hormones released | ADH/vasopressin and oxytocin. |
Hormone source | The hypothalamus produces them; the posterior pituitary stores and releases them. |
Main systems affected | Kidney water balance, uterus, mammary glands and vas deferens. |
What the research says
Central diabetes insipidus is fairly common after pituitary surgery, but it is usually temporary. A systematic review and meta-analysis of 51 studies found that, after transsphenoidal surgery for pituitary tumors, 17% (95% CI 13–21) of patients developed transient vasopressin deficiency (central diabetes insipidus) and 3% (95% CI 2–5) developed permanent deficiency. Permanent deficiency was 2% after surgery for pituitary adenomas, but 30% for craniopharyngiomas and 14% for Rathke’s cleft cysts (Fountas et al., Eur J Endocrinol, 2024). [2]
Vaptans raise blood sodium in SIADH, but they carry a risk of overcorrection. A systematic review and meta-analysis of five studies (three randomized trials and two cohort studies; 1,840 participants) found that vasopressin receptor antagonists, or vaptans, raised serum sodium by 4.77 mmol/L (95% CI 3.57–5.96) more than control on days 4–5. Overcorrection occurred in 13.1% of the vaptan group versus 3.3% of the control group, and no cases of osmotic demyelination syndrome were observed (Krisanapan et al., J Clin Med, 2023). [3]
What is the posterior pituitary?
The posterior pituitary is the back lobe of the pituitary gland. The pituitary gland is a small, pea-sized endocrine gland at the base of the brain below the hypothalamus. [1]
The pituitary gland has two lobes: the anterior, or front, lobe and the posterior, or back, lobe. The pituitary is part of the endocrine system, a network of glands that release hormones into the bloodstream. [1]
The posterior pituitary stores and releases only two of the many hormones associated with the pituitary gland: oxytocin and antidiuretic hormone, also called ADH or vasopressin. [1]
Where is the posterior pituitary located?
The pituitary gland is at the base of the brain, behind the bridge of the nose and directly below the hypothalamus. It sits in an indentation in the sphenoid bone called the sella turcica. [1]
The posterior pituitary is the back lobe, facing the back of the head. The anterior pituitary is in front of it and faces the front of the head. [1]
The pituitary gland connects to the hypothalamus through a stalk containing blood vessels and nerve cells. This is called the pituitary stalk. [1]
How does the posterior pituitary work with the hypothalamus?
The hypothalamus produces ADH and oxytocin. It sends nerve signals through the pituitary stalk to tell the posterior pituitary when to store and release these hormones. [1]
This arrangement means the posterior pituitary acts mainly as a storage and release site for these two hormones rather than as the place where they are produced.
Structure | Role |
Hypothalamus | Produces ADH and oxytocin and sends release signals. |
Pituitary stalk | Contains blood vessels and nerve cells and connects the hypothalamus with the pituitary. |
Posterior pituitary | Stores and releases ADH and oxytocin. |
What hormones does the posterior pituitary release?
The posterior pituitary stores and releases ADH and oxytocin. [1]
Antidiuretic hormone (ADH or vasopressin)
ADH helps regulate the body’s water balance. It does this by controlling how much water the kidneys reabsorb while they filter waste from the blood. [1]
Oxytocin
In females, oxytocin helps labor progress by contracting the uterus, causes breast milk to flow and influences bonding between mother and baby. In males, it can influence bonding between parent and baby and plays a role in ejaculation by contracting the vas deferens to push sperm and semen forward for ejection. [1]
Oxytocin affects the uterus, mammary glands and vas deferens. [1]
Hormone | Main effects |
ADH / vasopressin | Helps regulate water balance by controlling kidney water reabsorption. |
Oxytocin | Affects uterine contractions, milk flow, bonding and ejaculation-related vas deferens contraction. |
How big is the posterior pituitary?
The entire pituitary gland is about 1/3 of an inch in diameter, or approximately the size of a pea. The posterior pituitary is smaller than the anterior pituitary. The anterior pituitary makes up about 80% of the total weight of the pituitary gland. [1]
What conditions affect the posterior pituitary?
The main posterior-pituitary problems involve hypersecretion, meaning too much hormone, or hyposecretion, meaning too little hormone, of ADH or oxytocin. Most of these conditions are rare. [1]
Tumors can also affect the posterior pituitary, but they are rare. Pituitary tumors more commonly affect the anterior lobe. [1]
Hormone or issue | Possible pattern |
ADH deficiency | Too little ADH can impair kidney water reabsorption and cause central diabetes insipidus. |
Excess ADH | Too much ADH can cause SIADH and excessive water retention. |
Oxytocin deficiency | Rarely, too little oxytocin can affect uterine contractions and milk ejection during birth. |
Oxytocin excess | Very rarely, excess oxytocin can cause oxytocin toxicity and an overactive uterus. |
Tumors | Rarely affect the posterior pituitary; tumors more commonly involve the anterior lobe. |
What is central diabetes insipidus?
Central diabetes insipidus, or CDI, is a rare water-metabolism disorder that can result from a lack of ADH. It is not the same as diabetes mellitus and is not related to diabetes mellitus. [1]
Low ADH may happen when production by the hypothalamus or release from the pituitary decreases. It is usually caused by damage to the hypothalamus or posterior pituitary, and rarely by a gene mutation. In some cases, the cause is unknown. [1]
Without enough ADH, the kidneys do not reabsorb enough water. Urine becomes very diluted, while the blood becomes very concentrated. CDI can become life-threatening if it is not treated. [1]
Symptoms associated with central diabetes insipidus
Symptoms include frequent urination, extreme thirst, fatigue caused by waking several times overnight to urinate and dehydration. [1]
These symptoms can have other causes. They require professional assessment rather than self-diagnosis. [1]
What is SIADH?
Syndrome of inappropriate antidiuretic hormone secretion, or SIADH, can happen when the hypothalamus produces too much ADH or the posterior pituitary releases too much ADH. Excess ADH causes the body to retain too much water. [1]
This can make urine very concentrated and blood overly saturated with water, or diluted. Symptoms are most often caused by low blood sodium levels. [1]
Causes associated with excess ADH
Causes associated with SIADH or excess ADH include certain medications, such as some type 2 diabetes and anti-seizure medications, general anesthesia for surgery, brain injury, infections, stroke and brain surgery near the hypothalamus. [1]
Symptoms associated with excess ADH
Possible symptoms related to low blood sodium include nausea and vomiting, headache, balance problems that may lead to falls, and mental changes such as confusion and memory problems. [1]
What happens with too little oxytocin?
Too little oxytocin is rare. Lower-than-normal oxytocin can stop uterine contractions and milk ejection during the birthing process. [1]
Although rare, the most common cause of low oxytocin levels is panhypopituitarism, a condition in which all pituitary hormone levels are below normal. [1]
What happens with too much oxytocin?
Too much oxytocin is very rare and is called oxytocin toxicity. Higher-than-normal oxytocin, most often from oxytocin medicine given to start or speed up labor, can make the uterus contract too strongly or too often, which can stress the baby. Very high doses can also cause water retention and low blood sodium.
How are posterior-pituitary conditions tested?
If symptoms suggest a posterior-pituitary problem, a healthcare professional may order tests of ADH/vasopressin and/or oxytocin. [1]
An ADH blood test can help detect, diagnose and determine the cause of ADH deficiency or excess. Oxytocin levels can be tested in saliva, blood, plasma, urine or cerebrospinal fluid. [1]
If test results are abnormal, a healthcare professional may suggest an MRI to examine the pituitary gland. [1]
Evaluation | Purpose |
ADH blood test | Helps detect, diagnose and determine the cause of ADH deficiency or excess. |
Oxytocin testing | May use saliva, blood, plasma, urine or cerebrospinal fluid. |
MRI | May be suggested after abnormal results to examine the pituitary gland. |
When should you contact a healthcare professional?
Contact a healthcare provider if you have symptoms of central diabetes insipidus or SIADH.
New or concerning symptoms such as frequent urination, extreme thirst, dehydration, nausea, vomiting, headache, balance problems, confusion or memory changes should be discussed with a healthcare professional.
Because the same symptoms can occur with many conditions, an online article cannot identify the cause or determine an individual treatment.
Severe dehydration, confusion, a seizure, collapse, or rapidly worsening symptoms need prompt medical assessment.
How are posterior-pituitary conditions treated?
Posterior pituitary conditions have no single general treatment plan, so care should be discussed with a qualified healthcare professional. The appropriate care depends on the hormone involved, the cause, test results and severity.
Do not change fluids, medications or hormone treatment based on an online article. Discuss results and options with a qualified healthcare professional.
Conclusion: A small lobe with a large signaling role
The posterior pituitary is the back lobe of the pituitary gland. It stores and releases ADH and oxytocin, which are produced by the hypothalamus and delivered through the pituitary stalk. [1]
ADH supports kidney water reabsorption and body water balance. Oxytocin affects uterine contractions, milk flow, bonding and ejaculation-related vas deferens contraction. [1]
Most posterior-pituitary disorders are rare, but too little or too much ADH can affect hydration and blood sodium. Hormone testing and, when indicated, MRI can help professionals evaluate a concern. [1]
Use this guide to prepare questions for a qualified healthcare professional. Clear information is a starting point for better care—not a diagnosis. [1]
Frequently Asked Questions
What is the posterior pituitary?
The posterior pituitary is the back lobe of the pituitary gland, a small endocrine gland at the base of the brain below the hypothalamus.
What does the posterior pituitary do?
The posterior pituitary stores and releases ADH/vasopressin and oxytocin.
Does the posterior pituitary make its hormones?
No. The hypothalamus produces ADH and oxytocin, while the posterior pituitary stores and releases them.
What is ADH?
ADH, or vasopressin, helps regulate water balance by controlling how much water the kidneys reabsorb.
What is oxytocin?
Oxytocin is a hormone released by the posterior pituitary that helps labor progress, causes milk to flow, influences bonding and plays a role in ejaculation.
Where is the posterior pituitary located?
The posterior pituitary is at the base of the brain as the back lobe of the pituitary gland, below the hypothalamus and behind the bridge of the nose.
What is the pituitary stalk?
The pituitary stalk is a stalk containing blood vessels and nerve cells that connects the hypothalamus with the pituitary gland.
What is central diabetes insipidus?
Central diabetes insipidus is a rare water-metabolism disorder caused by a lack of ADH. It is distinct from and unrelated to diabetes mellitus.
What are symptoms of central diabetes insipidus?
Symptoms include frequent urination, extreme thirst, fatigue and dehydration.
What is SIADH?
SIADH is a condition associated with excess ADH, causing the body to retain too much water.
What are symptoms of excess ADH?
Symptoms related to low blood sodium can include nausea, vomiting, headache, balance problems, confusion and memory problems.
Are posterior-pituitary disorders common?
Most conditions related to the posterior pituitary are rare.
Can tumors affect the posterior pituitary?
Yes, but tumors are rare there; pituitary tumors more commonly affect the anterior lobe.
How is ADH tested?
An ADH blood test can help detect, diagnose and determine the cause of ADH deficiency or excess.
How is oxytocin tested?
Oxytocin may be tested in saliva, blood, plasma, urine or cerebrospinal fluid.
Is an MRI used for posterior-pituitary problems?
If hormone test results are abnormal, a healthcare professional may suggest an MRI to examine the pituitary gland.
When should I contact a healthcare professional?
Contact one for symptoms of central diabetes insipidus or SIADH, or for new or concerning symptoms such as frequent urination, extreme thirst, dehydration, nausea, headache, confusion or balance problems.
Related guides
Related guides on the pituitary gland, hypothalamus, endocrine system, kidney anatomy and central diabetes insipidus can help explain the posterior pituitary.
References
Cleveland Clinic. Posterior Pituitary: What It Is & Function. Cleveland Clinic. Updated June 1, 2022. https://my.clevelandclinic.org/health/body/23150-posterior-pituitary
Fountas A, Coulden A, Fernández-García S, et al. Central diabetes insipidus (vasopressin deficiency) after surgery for pituitary tumours: a systematic review and meta-analysis. Eur J Endocrinol. 2024;191(1):S1-S13. PMID 38996052. https://doi.org/10.1093/ejendo/lvae084
Krisanapan P, Tangpanithandee S, Thongprayoon C, et al. Safety and Efficacy of Vaptans in the Treatment of Hyponatremia from Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH): A Systematic Review and Meta-Analysis. J Clin Med. 2023;12(17):5483. PMID 37685548. https://doi.org/10.3390/jcm12175483
Medical disclaimer
This article is for general educational purposes and is not a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified healthcare professional with any questions about a medical condition or treatment.
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