SIADH vs Diabetes Insipdius! Are you studying diabetes insipidus and SIADH and find it very confusing discerning between the two disease processes? You are not alone!
In this article, I am going to easily break down the differences between diabetes insipidus (DI) and SIADH (Syndrome of Inappropriate Anti-diuretic Hormone). I addition, I provide a lecture on how to remember the differences between the two!
Don’t forget to take the SIADH vs Diabetes Insipidus Quiz.
What is Diabetes Insipidus and SIADH?
This is where the body has a problem producing ADH (either too much or not enough). What is ADH? It is anti-diuretic hormone. This hormone is produced in the hypothalamus, and stored and eventually released in the posterior pituitary gland. In order to understand diabetes insipidus and SIADH, you MUST understand how ADH works because ADH plays an important role in both DI an SIADH.
Lecture on SIADH and DI
Key Points to Remember about SIADH and DI
- Each condition is related the secretion of ADH (anti-diuretic hormone also called vasopressin) which plays a major role in how the body RETAINS water.
- Each condition presents oppositely of each other (ex: in SIADH the patient retains water vs. DI where the patient loses water)—-Remember they are opposite of each other!
- Diabetes Insipidus and Diabetes Mellitus are two separate conditions and are not related although they share the name “Diabetes”.
How does the Anti-diuretic Hormone work?
ADH is produced in the hypothalamus and secreted/stored by the posterior pituitary gland. The function of ADH is to cause the body to retain water and constrict blood vessels.
How ADH cause the body to retain water? Through the help for the KIDNEYS! ADH causes the renal tubules to retain water (in a homeostatic way). ***But if you have too much ADH you will retain too much water and if you have too little ADH you will urinate all of the water our of your body!
How to Remember which one is Increased vs Decreased?
Syndrome of Inappropriate Antidiuretic Hormone (SIADH): There is a high level of ADH (antidiuretic hormone) produced
I like to remember this by the acronym SIADH….S Increased ADH (anti-diuretic hormone)
High Level of ADH equals low urinary output
Diabetes Insipidus: There is a low level of ADH (antidiuretic hormone) produced
Low Level of ADH equals excessive urinary output
Diabetes Insipidus Key Concepts
Causes of Diabetes Insipidus:
- Kidneys not receptive to ADH
- Damage to the pituitary gland and/or hypothalamus
- Brain trauma through stroke or head trauma
- Drugs… ex: Declomycin: this is a part of the tetracyline antibiotic family and has properties to inhibit ADH production and is also a treatment for SIADH
- Gestational due to the placenta producing vasopressinase….too much vasopressinase causes ADH to breakdown
Signs and Symptoms of DI
- Polyuria: LOTS of urine 4L to 24 L per day
- Polydipsia: body’s way of trying to keep water in the body….crave water/ice
- Dry mucous membranes, dry skin, decrease skin tugor…very dehydrated
- Urine diluted….low urinary specific gravity
- Hypotension (due to the severe dehydration and remember ADH is responsible for constricting blood vessels…here the vessel will be dilated which causes hypotension)
- Extreme fatigue and muscle pain/weakness
- Hypernatremic (due to the concentrate sodium in the body from low water levels)
Nursing Management of Diabetes Insipidus
- Strict I and O’s, daily weights, safety, watch other electrolytes (hypokalemia)
- Restrict foods that promote diuresis: watermelon, grapes, garlic, berries etc and caffeine (tea, energy drinks, coffee)
- MD may order:
- Mild cases: Chlorpropamide aka Diabinese (used in type 2 diabetes…not used as much now but it has properties that increases ADH hormone…watch for hypoglycemia (blood glucose) and educate patient about photo-sensitivity to the sun (mild)
- Extreme cases: Desmopression (form of vasopressin that naturally occurs in the body which the ADH) also called Stimate or DDAVP…given PO, IV, nasally, or subq. Side Effects: Watch for the patient to become hyponatremic too and water intoxication
Syndrome of Inappropriate Antidiuretic Hormone (SIADH)
Try to remember it by this:
Causes of SIADH
- Lung cancer (may be a first sign a patient gets…then finds out they have lung CA)
- Damaged to the hypothalamus or pituitary gland
- Infection/germs (PNA, meningitis)
- Central neuro issues: strokes, gullian-barre syndrome
- Drugs (Diabinese aka Chlorpropamide which has properties to increase the ADH and is a treatment for DI)
Signs and Symptoms of SIADH
- Fluid overload (weight gain)
- Fast HR
- Low sodium (euvolemic hyponatremia…sodium is watered down)
- Confusion (due to brain swelling with extra fluid)
- Anorexia (full of water…doesn’t want to eat)
- Low urine output with concentrated urine (high urinary specific gravity)
Nursing Management of SIADH
- Daily weights and watch for weight gain, strict intake and output, fluid restrictions, safety (confused from brain swelling and low sodium)
- Medical treatment per md order:
- Loop Diuretics (Lasix): to remove the extra fluids through the kidneys…watch K+ levels
- Hypertonic IV solutions (3% Saline) to remove fluid from the cell back into the vascular system so it can be urinated out (watch for causing fluid volume overload..give slowly and through central line per hospital protocol)****NOTE: Loop Diuretics & Hypertonic Solutions are usually order together.
- Declomycin (tetracycline family) ADH inhibitor and allow for diuresis…don’t give with calcium containing foods like milk or antacids because it affects absorption.
Still Confused on the Differences between Diabetes Insipidus & Syndrome of Inappropriate Antidiuretic Hormone (SIADH)?
Here is a chart comparing the two. You can use this as a study aid in helping you remember. Sometimes, seeing the differences side by side between the two helps.