He has hypothyroidism, diabetes, and hypertension. Last summer he was admitted to the ICU for severe hyponatremia (after a 4 day period of febrile illness). Several investigations we done, no specific cause was found (no infection, no malignancies and no adrenal insufficiency). It was decided it was caused by malnutrition and colonic irrigation that was done 4 days in a row.
This summer he has been complaining of fatigue for 4 days associated with worsened back pain. Routine investigations were done, including electrolytes. His Na is 132 mEq/L.
The patient complains frequently that he feels cold. He is always overdressed. The past few days have been extremely hot, temperatures ranged between (33-36C). According to his family he has been overdressed, and covers himself with heavy blankets. The bed and blankets are wet with sweat. He almost drinks 2.5L of water daily.
*40 days ago his Na level was 134 mEq/L, his water intake was restricted and his Na levels became within normal range within a few days.
*His antihypertensive medication has no diuretic. He has a sessile colonic polyp discovered almost a year ago.
Could his hyponatremia possibly be caused by excessive sweating and high water intake? (Mimicking Exercise-Associated hyponatremia in athletes).
Urine sodium in this patient is ~ 50 mMol/L. In presence of hyponatremia a urine Na of > 20 mMol/L is suggestive of relative excess of volume due to Inappropriate secretion of Antidiuretic hormone or Hypothyroidism, or Glucolorticoid deficiency or Stress.
In this patient hypothyroidism is already present. Stress also may be a factor. SIADH can't be ruled out at the moment.
If it is purely due of sweating (extrarenal losses) Urine Na should be < 20 mMol/L.
Water restriction to < 1 liter per day should correct hyponatremia in this patient. Also, correction of hypothyroidism will be needed.
I sugest to repeat investigations to exclude adrenal insufficiency (back pain, fatigue, hyponatremia after the febrile illness and in summer (hot days?)).
I agree that adrenal insufficiency has to be ruled out. But, hypothyroidism and hyperglycemia can also cause hyponatremia.
I believe he needs some rest during summer specially with the current high temperature weather.
Adrenocortical insufficiency and diuretic were ruled out as the source of hyponatremia. Malnutrition, unexplained fever may be paraneoplastic expressions from the colonic polyp.
Today his serum Na is 129 mEq/L (2 days ago it was 132 mEq/L).
His family report he's well, slightly tired. But his activity level is as usual. However, yesterday he has been overdressed (as ususal) and when sleeping covers himself in heavy blankets and sweats heavily.
Today his Serum Na is 128mEq/L
His Serum Osmolality is 255 mOsmol/L (280-303 mOsmol/L)
His 24-hr urine Na is 204mmol/24hr (40-220mmol/24hr)
Urine Volume in 24 hrs was 4040ml
I agree with you that the hyponatremia is due to excessive sweating & high water intake . He also has polyuria with salt loss ( salt losing nephropathy ) , probably due to chronic Interstitial nephritis . The symptoms may be due to salt depletion . This is probably hypovolemic hyponatremia & he needs more than 10 gms of salt per day . Please measure his urine osmolarity . He may be taking less salt due to hypertension .
Though hypothyroidism, diabetes, and drugs for hypertension can all cause low Na, I think multiple myeloma also needs exclusion as he is having back pain with kidney involvement [high ESR and globulin levels followed by bone marrow biopsy, SERUM PROTEIN ELECTROPHORESIS]
You could check the urine specific gravity . How are his renal functions . I would expect him to have reduced urine output , because of his sweating & volume depletion . But his polyuria is also contributing to fluid & sodium loss . Has an abdominal ultrasonogram done to rule out renal disease ( obstructive nephropathy ) , which can cause polyuria . What is his serum K level .
Urine sodium in this patient is ~ 50 mMol/L. In presence of hyponatremia a urine Na of > 20 mMol/L is suggestive of relative excess of volume due to Inappropriate secretion of Antidiuretic hormone or Hypothyroidism, or Glucolorticoid deficiency or Stress.
In this patient hypothyroidism is already present. Stress also may be a factor. SIADH can't be ruled out at the moment.
If it is purely due of sweating (extrarenal losses) Urine Na should be < 20 mMol/L.
Water restriction to < 1 liter per day should correct hyponatremia in this patient. Also, correction of hypothyroidism will be needed.
We need to explain why he has polyuria ( urine volume ; 4040 ml ) . Urine sodium of 204 mmol/day suggests a loss of 12gms /day ( 204/17 = 12 ; 1gm of Nacl = 17gms ) . If there is sodium loss due to renal loss , then urine sodium > 20mmol/day . This patient is not on diuretics . In addition , sodium loss is also due to sweating .
Polyuria may occur in chronic interstitial nephritis which might also explain his salt loss
Dilutional hyponatremia and hypothyroidism are both possible causes
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