Diabetes Insipidus vs SIADH: All you Need to Know

In this article, I will be discussing two disorders, diabetes insipidus and syndrome of inappropriate ADH (SIADH). These disorders result from improper amounts of ADH in the body, so begin with a quick review of ADH. I will discuss the causes, symptoms, diagnosis, and treatment for these two medical conditions.

What is ADH?

ADH is a hormone released by the posterior pituitary gland in response to conditions such as

  1. Low blood volume
  2. Low blood pressure
  3. Increased blood osmolality (Hypernatremia)

These conditions when sensed by the body causes it to release ADH from the posterior pituitary gland, which will cause. the kidneys to reabsorb more water, which helps to

  • Increase blood volume
  • Increase blood pressure
  • Dilute the blood so the blood osmolality drops to a normal level

Diabetes Insipidus

When diabetes insipidus(DI) occurs, the body releases a too less anti-diuretic hormone (ADH). It is a disorder of water and salt metabolism marked by extreme thirst and heavy urination. Per day it is common to make 1 to 3 quarts of urine but people with diabetes insipidus can make urine a day up to 20 quarts. This condition takes place when the body is unable to regulate the fluids and is caused by a hormonal abnormality and is not related to diabetes.


The types of diabetes insipidus include;

Central Diabetes Insipidus.

This is damage to the pituitary gland or hypothalamus from surgery, a tumor, head injury, or illness that can cause central diabetes insipidus by affecting the usual production, storage, and release of ADH, also an inherited genetic disease also can cause this condition.

Nephrogenic Diabetes Insipidus:

Nephrogenic diabetes insipidus occurs when there’s a defect in the structures in your kidneys that makes your kidneys unable to properly respond to ADH. Certain drugs, such as lithium or antiviral medications such as foscarnet can also cause nephrogenic diabetes insipidus.

Gestational Diabetes Insipidus:

Gestational diabetes insipidus is rare. It occurs only during pregnancy when an enzyme made by the placenta destroys ADH in the mother.

Primary Polydipsia:

Also known as dipsogenic diabetes insipidus, this condition can cause the production of large amounts of diluted urine from drinking excessive amounts of fluids.

Primary Polydipsia:

This can be caused by damage to the thirst-regulating mechanism in the hypothalamus. The condition has also been linked to mental illness, such as schizophrenia

Causes of Diabetes Insipidus(DI)

The causes of diabetes insipidus include:

  • When the Kidneys are not receptive to antidiuretic hormone secretion (ADH)
  • Brain damage or trauma through head injury or stroke
  • Tumors
  • Harm to the hypothalamus and/or the pituitary gland
  • Drugs like Declomycin. This drug inhibits ADH production.
  • Complications that happen during pituitary surgery or brain
  • Gestational due to the placenta producing vasopressinase which causes ADH to breakdown


Persons with Diabetes insipidus may experience;

  1. Too much thirst
  2. Increased urge to urinate especially during the night
  3. Producing huge amounts of diluted urine

Meanwhile, children or infants with Diabetes insipidus may experience

  1. Wet and heavy diapers
  2. Sleeping disorders
  3. Fever
  4. Low blood pressure (hypotension)
  5. Acute constipation
  6. Weight loss
  7. Accelerated heart rate
  8. Bed-wetting
  9. Delayed growth
  10. Puking


Diabetes insipidus(DI) can be diagnosed using several tests methods which may include:

  1. Physical examination
  2. Urine analysis
  3. Medical history
  4. Water deprivation test (to find out how much urine is passed)
  5. Assessment of electrolyte levels – Blood tests
  6. Computed tomography (CT) scans.
  7. Magnetic resonance imaging (MRI) scan of the brain.


The treatment of this condition depends on the type of diabetes insipidus you have.

Central Diabetes Insipidus:

If you have mild diabetes insipidus, you may need only to increase your water intake. If the condition is caused by an abnormality in the pituitary gland or hypothalamus and can be treated with a synthetic hormone called desmopressin, which replaces the missing anti-diuretic hormone (ADH) and decreases urination.

You can take desmopressin in a tablet, as a nasal spray, or by injection. Most people still make some ADH, though the amount can vary day to day. So, the amount of desmopressin you need also may vary. Taking more desmopressin than you need can cause water retention and potentially serious low-sodium levels in the blood. Other medications such as chlorpropamide may also be prescribed. This can make ADH more available in the body.

Nephrogenic Diabetes Insipidus:

Since the kidneys don’t properly respond to ADH in this form of diabetes insipidus, desmopressin won’t help. Instead, your doctor may prescribe a low-salt diet to reduce the amount of urine your kidneys make. You’ll also need to drink enough water to avoid dehydration. Treatment with the drug hydrochlorothiazide (Microzide) may improve your symptoms.

Although hydrochlorothiazide is a type of drug that usually increases urine output (diuretic), it can reduce urine output for some people with nephrogenic diabetes insipidus. If your symptoms are due to medications you’re taking, stopping these medicines may help. However, don’t stop taking any medication without first talking to your doctor.

Gestational Diabetes Insipidus:

Treatment for most people with gestational diabetes insipidus is with the synthetic hormone desmopressin.

Primary Polydipsia:

There is no specific treatment for this form of diabetes insipidus, other than decreasing fluid intake. If the condition is related to a mental illness, treating the mental illness may relieve the diabetes insipidus symptoms.


SIADH stands for Syndrome of Inappropriate Antidiuretic Hormone secretion. This is a medical condition where there is an excessive level of antidiuretic hormone (ADH) production by the body and due to this higher concentration of ADH, the body retains a huge amount of water.

This process alters the mineral (electrolytes) balance in the body, particularly sodium. ADH assists the kidneys to control the quantity of water the body loses through the urine. Syndrome of the inappropriate antidiuretic hormone causes the body to regent excess water in the body. The resulting water secretion impairment and consequent water retention produce hyponatremia.

Causes of SIADH

There are several things that can cause a Syndrome of Inappropriate Antidiuretic Hormone secretion which may include:

  1. Liver disease
  2. Hypothyroidism
  3. Adrenal insufficiency
  4. Eco-topic tumor production
  5. Pulmonary disease/lung cancer

Guillain-Barré syndrome is a medical condition that is reversible and impacts the nerves in the body which can lead to muscle pain, weakness, and temporary paralysis of the chest, facial, and leg muscles. Paralysis of the chest muscles can lead to breathing disorders.


Persons with Syndrome of Inappropriate Antidiuretic Hormone secretion(SIADH) may experience things like;

  1. Vomiting or nausea
  2. Depressed mood, memory impairment
  3. Tremors or cramps
  4. Irritability
  5. Seizures
  6. Personality changes such as confusion, combativeness, and hallucinations.


Syndrome of Inappropriate Antidiuretic Hormone secretion(SIADH) can be diagnosed using any of the following tests.

  • Biochemistry tests to know the serum sodium level
  • Urine osmolality
  • Thyroid function tests
  • Early morning cortisol level
  • Computed tomography (CT) of the head in case of a neurosurgical condition
  • Chest X-ray in case SIADH is caused due to pulmonary reasons.


Loop Diuretics:

This helps to remove the extra fluids through the kidney.

Hypertonic IV solutions (3% Saline) remove fluid from the cell back into the vascular system so it can be urinated out.

Restriction in Fluid Intake:

Doctors restrict fluid intake and treat the cause if possible. People with SIADH need treatment for hyponatremia in the long term.

Intravenous fluids, including fluids containing very high concentrations of sodium (hypertonic saline), are sometimes given. Such treatments must be given carefully to avoid rapid increases in the sodium level.

If the sodium level in the blood continues to decrease or does not increase despite restriction of fluid intake, doctors may prescribe some drugs such as demeclocycline or lithium, which help decrease the effect of vasopressin on the kidneys, which block vasopressin receptors and prevent the kidneys from responding tovasopressin.

Diabetes Insipidus vs SIADH

Diabetes Insipidus (DI), as well as Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH), are both disorders of water regulation causing the release of anti-diuretic hormone (ADH) in the body.

Whereas in SIADH, there is a significant electrolyte abnormality and water retention due to the inability to suppress the Antidiuretic hormone. In Diabetes insipidus (DI), there is either lowered production of an Antidiuretic hormone known as central DI or normal Antidiuretic hormone secretion with resistance in the kidneys to its impacts known as nephrogenic Diabetes insipidus. A huge amount of dilute urine diuresis can result from Diabetes insipidus.

Difference Between Diabetes Insipidus and SIADH

Diabetes Insipidus is a medical condition or disorder of water and salt metabolism characterized by heavy urination and intense thirst. While SIADH means Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) and is a disorder that is characterized by an increased and insuppressible release of ADH either from an abnormal non-pituitary source or posterior pituitary gland. This unsuppressed Antidiuretic hormone causes an elevation in solute-free water getting returned by the tubules of the kidney to the venous circulation.

Diabetes Insipidus VS SIADH


The main difference between diabetes insipidus and SIADH is that Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) is a disorder of hormones that has an increased level that causes retention of water, whereas diabetes insipidus is a disorder of salt and water metabolism characterized by intense thirst as well as heavy urination.

Egbujor Victor Chinedu
He Is Just A Pro Blogger Who Invests his time in Blogging and Web Designing ... Student, Writer...

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