Difference Between Diabetes Insipidus and SIADH

In the body, the role of the regulation of levels of water is to the kidney. In case of dehydration, they simply conserve water, and to expel excess water they can make urine. Also, through skin surface evaporation takes place which causes loss of water without even overt sweating.  

Sometimes imbalance of water regulation leads to disorders like DI or diabetes insipidus and SIADH or syndrome of inappropriate antidiuretic hormone secretion. These disorders directly impact the activity or release of ADH. In this article, the main focus is on differentiating diabetes insipidus and SIADH. 

Diabetes Insipidus vs SIADH 

The main difference between diabetes insipidus and SIADH is that diabetes insipidus is a disorder of salt and water metabolism marked by intense thirst as well as heavy urination. Meanwhile, SIADH is a disorder of hormone increase level which causes water to retain. 

Diabetes Inspidus vs SIADH

Among the rare disorders, diabetes insipidus is one of them which causes too much making of urine. 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 disorder makes people two frequently urinate. 

The abbreviation for the syndrome of inappropriate antidiuretic hormone secretion is SIADH. It generally involves the continued action or secretion of AVP or arginine vasopressin despite increased or normal plasma volume. The resulting water secretion impairment and consequent water retention produce hyponatremia. 

Comparison Table Between Diabetes Insipidus and SIADH 

Parameters of ComparisonDiabetes InsipidusSIADH
InterpretationIt is a condition in which salt and water metabolism is marked by intense thirst as well as heavy urination.It is a condition of hormone increase level which causes water to retain. 
Sodium contentHighLow
ADHInadequateExcess
Plasma volumeEuvolemicSlightly hypervolemic or euvolemic
RiskHypovolemic shockSeizures

What is Diabetes Insipidus?  

Diabetes insipidus is one of the uncommon disorders that causes in the body an imbalance of fluids. This imbalance results from the production of urine in mainly large amounts. Even if the person has something to drink but still makes the patient very thirsty. Diabetes insipidus is sometimes confused with diabetes mellitus because they sound similar.  

Meanwhile, diabetes mellitus is a completely different disorder that is common and involves a high level of blood sugar. Diabetes insipidus has particularly no cure but treatment can relieve thirst and prevent dehydration as well as decrease output of urine. It generally occurs when the body fails to properly balance the fluid levels.  

Sometimes, for diabetes insipidus, there is no particular cause. But in some people, the result might be due to a reaction of autoimmune that leads to damaging of cells due to the immune system that makes vasopressin. Dehydration can be led by diabetes insipidus which can be caused by dry mouth, fatigue, and thirst.  

Nephrogenic diabetes insipidus shortly after or present at birth generally has a genetic cause that can permanently change the ability of the kidney to the concentration of urine. It generally affects males, but genes can be passed to children by women. 

What is SIADH? 

ADH or anti-diuretic hormone is specifically produced by the hypothalamus which is an area of the brain. This hormone is released and stored by the gland namely, the pituitary. The main goal of ADH is to control how the body conserves or releases the water.  

When in excess amount, the ADH is released this condition is known as SIADH or simply syndrome of inappropriate antidiuretic hormone. This condition makes it harder for to water be released by the body.  Additionally, SIADH causes electrolytes levels, like sodium to fall due to water retention.  

Hyponatremia or simply low sodium level is a SIADH’s major complication and is also responsible for various symptoms related to SIADH. When it comes to early symptoms, its symptoms might be mild and consist of vomiting, cramping, and nausea.  

SIADH can also cause coma, confusion, and seizures in many severe cases. Treatment generally begins with fluid intake in a limited amount to prevent its buildup in further amounts. Depending on the causes, its additional treatment relies on. 

Main Differences Between Diabetes Insipidus and SIADH 

  1. Diabetes insipidus can be classified into NDI or nephrogenic diabetes insipidus and CDI or cranial diabetes insipidus. Conversely, SIADH can be classified into Type D SIADH, Type B SIADH, Type C SIADH, and Type A SIADH.  
  2. The causes for diabetes insipidus are brain damage due to stroke, complications during pituitary surgery, and drugs like Declomycin. On the other hand, adrenal insufficiency, mental status changes, and pulmonary disease are causes of SIADH.  
  3. These symptoms of diabetes insipidus are cold drinks cravings, too much thirst, huge diluted urine production, and during the night increased urge to pee. Meanwhile, seizures, vomiting, irritability, and memory impairment are SIADH symptoms.  
  4. Tests included in diabetes insipidus diagnosis are water deprivation test, physical examination, urine analysis, and electrolyte levels assessment. In contrast, biochemistry tests, serum osmolality, early morning cortisol level, and thyroid function tests are tests included in SIADH diagnosis.  
  5. When it comes to treatment, diabetes insipidus can be treated with HCTZ, vasopressin, and chlorpropamide. On the flip side, SIADH can be treated by demeclocycline, fluid restriction, and normal saline. 

Conclusion 

It can be concluded that diabetes insipidus and SIADH are two of the water regulation disorder which directly impacts the activity or release of ADH or anti-diuretic hormone in the body. When it comes to sodium content, it is higher in diabetes insipidus, whereas sodium content is lower in SIADH. Plasma volume is euvolemic in diabetes insipidus. In contrast, slightly hypervolemic or euvolemic is the plasma volume in SIADH.  

In diabetes insipidus, too little antidiuretic hormone is produced. It usually means the production of ADH shortage, which can be against diuresis and results in polyuria. On the other hand, SIADH disorder fails to produce water as much it should and secretes ADH in a large amount. 

References  

  1. https://www.sciencedirect.com/science/article/pii/S0889852918300318
  2. https://journals.sagepub.com/doi/abs/10.1177/2042018812437561
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