Diabetes Insipidus vs Siadh

Diabetes insipidus and Syndrome of Inappropriate Anti-diuretic Hormone [SIADH] have some similarities, but are two very different conditions. They both involve how the body create vasopressin [ADH] and one of the primary symptoms of both conditions is excessive thirst, but the results are completely the opposite. In diabetes insipidus, the body is excreting too many fluids as urine, which can often leave people feeling dehydrated. In SIADH, a person is retaining too much water instead.

Because the signs and symptoms can be somewhat similar, even if the body is either retaining too much water or too little, then here are some of the differences in these two opposite conditions that involve ADH.

What Is ADH and Why Is It Important?

Vasopressin is an anti-diuretic hormone. It is used by the body to regulate how much water is in the body at any given time. The kidneys are told to hang onto water or told to get rid of it. It can also create increased blood pressure levels because of vasoconstriction.

But, to make matters even more confusing, people who are suffering from liver cirrhosis may have inappropriate ADH levels that is similar to diabetes insipidus, but not actually the condition itself. Meningitis and encephalitis can also be the cause of diabetes insipidus or cause SIADH.

All of this is regulated by the posterior pituitary, though nephrogenic diabetes insipidus is caused by the kidneys. Treatment involves finding the cause of the condition and resolving it or reducing bothersome symptoms.

Different Causes for Different Conditions

SIADH is typically an issue which occurs when there is another disease going on. For patients with lung cancer, SIADH can actually be one of the first symptoms that are experienced. Remember – there is too much fluid being retained by the body. Damage to the pituitary gland or the hypothalamus, infections, certain neurological issues, and some medications are also known to cause SIADH.

SIADH always causes fluid overloads. This might be cause edema or weight gain. A faster heart rate, hypertension, low sodium levels, and highly concentrated urine are common symptoms that can be seen with this condition.

In diabetes insipidus, urine concentrations are never high. It creates a very dilute urine that can be in high amounts. Some patients with diabetes insipidus can pass up to 6 gallons of urine per day. You’ll see lower blood pressure, high sodium levels, and the signs and symptoms of dehydration present. A person with diabetes insipidus can become severely dehydrated in as little as 6 hours.

How You Can Tell The Difference of Diabetes Insipidus vs SIADH

Diabetes Insipidus: High urinary outputs, low levels of ADH, high sodium levels, high serum osmolality, ongoing dehydration, and high levels of fluid loss. There may also be a genetic cause for this condition.

SIADH: Low urinary outputs, high levels of ADH, low sodium levels, low serum osmolality, being over-hydrated, and retaining too many fluids. It is almost always caused by external factors. According to the National Institutes of Health, about 30% of hospitalized patients will experience these symptoms.

How To Treat Diabetes Insipidus vs. SIADH

Identifying the correct disorder is absolutely necessary because the wrong treatment plan could leave a patient with life-threatening results. If someone is suffering from SIADH and they are encouraged to retain even more water, then the resulting edema, weight gain, and stress on the kidneys could be very difficult. If diabetes insipidus is the issue and diuretics are administered to encourage even more fluid loss, dehydration could set-in within an hour or two.

Both conditions can be relatively managed when an appropriate diagnosis has been achieved. The testing processes, from urinary osmolality to serum osmolality to electrolyte blood tests, are the same for diabetes insipidus and SIADH. The results reported will then help a medical provider be able to determine the appropriate course of treatment.

In many instances, both conditions will also begin to become less severe when the underlying condition causing them can be effectively treated.

It can be somewhat confusing to know the differences between diabetes insipidus vs. SIADH when all that is examined are the initial symptoms. This is why further testing is always required, since excessive thirst can also be a symptom of diabetes mellitus in addition to these two health issues.

If you’re concerned about bothersome signs and symptoms that are being experienced right now, then schedule an appointment with your medical provider and discuss this guide. Ask about what tests are right for you. This will help you set a course toward being able to take charge over your health so these symptoms can be potentially treated so they become manageable.