Pathogenesis (development of disease)
Forms of hyponatremia:
- Hypertonic hyponatremia: in the presence of increased concentrations of other osmotically effective substances, usually glucose. The osmotic gap is greater than 10 mosmol/L.
- Hyponatremia in polydipsia (excessive thirst).
- Hyponatremia in euvolemia (total body sodium in the normal range).
- Urine Na+ > 30 mmol/L
- Syndrome of inadequate ADH secretion (SIADH) (synonym: Schwartz-Bartter syndrome) – there is an inappropriately high secretion of antidiuretic hormone (ADH; ADH excess) in relation to blood plasma osmolality; this leads to inadequate renal fluid excretion with the formation of highly concentrated urine; the result is hyperhydration (overhydration) with dilutional hyponatremia (“dilutional sodium deficiency”), which can lead to cerebral edema (brain swelling). Etiology (causes): paraneoplastic in approximately 80% of cases in patients with small cell lung cancer; other possible causes include:
- CNS (central nervous system) diseases: intracranial hemorrhage (bleeding within the skull; parenchymal, subarachnoid, sub- and epidural, and supra- and infratentorial hemorrhages)/intracerebral hemorrhage (ICB; brain hemorrhage), brain tumors, Guillain-Barré syndrome, infections, meningitis (meningitis), encephalitis (brain inflammation), multiple sclerosis (MS)
- Pulmonary diseases (lung diseases): pneumonia (pneumonia/insb. Legionella pneumonia (pneumonia caused by the pathogen Legionella pneumophilia)), bronchial carcinoma (small cell and non-small cell), emphysema (lung hyperinflation), chronic obstructive pulmonary disease (COPD), tuberculosis.
- Malignant (malignant) diseases: Carcinomas (lung, ENT area, gastrointestinal and genitourinary tract gastrointestinal tract and urinary and genital tract), lymphomas, sarcomas.
- Medications: Antidepressants, antiepileptics, anticonvulsants, antipsychotics, nonsteroidal anti-inflammatory drugs (NSAIDs), opioids.
- Miscellaneous: Vasopressin-2 receptor mutations, giant cell arteritis, idiopathic.
Symptoms: Nausea (nausea), loss of appetite, cephalgia (headache) posed.
- Syndrome of inadequate ADH secretion (SIADH) (synonym: Schwartz-Bartter syndrome) – there is an inappropriately high secretion of antidiuretic hormone (ADH; ADH excess) in relation to blood plasma osmolality; this leads to inadequate renal fluid excretion with the formation of highly concentrated urine; the result is hyperhydration (overhydration) with dilutional hyponatremia (“dilutional sodium deficiency”), which can lead to cerebral edema (brain swelling). Etiology (causes): paraneoplastic in approximately 80% of cases in patients with small cell lung cancer; other possible causes include:
- Hypercorticism
- Hypothyroidism (underactive thyroid gland)
- Water intoxication (water hydration; overhydration): in this case, the osmolarity in the urine is less than in the serum
- Primary polydipsia (excessive thirst; “psychogenic polydipsia”).
- Excessive intake of hypotonic solutions
- After transurethral resection of the prostate (TURP).
- Sports extreme loads
- Urine Na+ > 30 mmol/L
- Urine Na+ < 30 mmol/L
- As under the previously mentioned causes with concomitant low salt intake.
- Hyponatremia in hypovolemia (decrease in the amount of blood circulating, i.e., in the bloodstream).
- Urine Na+ > 30 mmol/L
- Addison’s disease (adrenocortical insufficiency)
- Salt wasting kidney
- Cerebral salt wasting syndrome (e.g. post SAB (subarachnoid hemorrhage)).
- Diuretics (dehydrating drugs) (loop diuretics).
- Urine Na+ < 30 mmol/L perspiratio insensibilis, burns/burns.
- Urine Na+ > 30 mmol/L
- Hyponatremia in hypervolemia (increase in the volume of circulating blood, i.e., in the bloodstream).
- Urine Na+ > 30 mmol/L
- Chronic renal failure – process leading to a slowly progressive reduction in renal function.
- Urine Na+ < 30 mmol/L
- Heart failure (cardiac insufficiency)
- Liver cirrhosis (irreversible (non-reversible) damage to the liver associated with marked remodeling of liver tissue) with ascites (abdominal dropsy) (liver failure)
- Nephrotic syndrome – collective term for symptoms that occur in various diseases of the glomerulus (renal corpuscles); the symptoms are proteinuria (increased excretion of protein in the urine) with a loss of protein; hypoproteinemia, peripheral edema (water retention) due to hypoalbuminemia (decreased level of albumin in the blood), hyperlipoproteinemia (lipid metabolism disorder).
- Urine Na+ > 30 mmol/L
While intracellular (“inside the cells”) sodium concentration is controlled by Na+/K+-ATPase, regulation of sodium concentration of the extracellular space (space outside the cells) is via the renin-angiotensin-aldosterone system (RAAS) and atrial natriuretic peptide (ANP). For details, see saline/regulation of sodium homeostasis.
Etiology (Causes)
Behavioral causes
- Diet
- Increased fluid intake (water intoxication).
- Inadequate intake of sodium and table salt.
- Micronutrient deficiency (vital substances) – sodium
- Consumption of stimulants
- Alcohol (in this case, elderly people with long-term malnutrition + more than five liters of beer every day → 4.5 percent of patients with hyponatremia and values below 135 mmol/l;1.3 percent) of patients showed severe hyponatremia (below 125 mmol/l), the lowest value was 104 mmol/l)
- Drug use
- Ecstasy (also XTC, Molly, etc.) – methylenedioxymethylamphetamine (MDMA); dosage on average 80 mg (1-700 mg); structurally belongs to the group of amphetamines.
Disease-related causes.
Endocrine, nutritional and metabolic diseases (E00-E90).
- Hypercorticism (Cushing’s disease: hypercortisolism; excess of cortisol).
- Hypothyroidism (hypothyroidism).
- Adrenocortical insufficiency (NNR insufficiency; adrenocortical weakness).
- Syndrome of inadequate ADH secretion (SIADH; there is an inappropriately high secretion of antidiuretic hormone (ADH) in relation to blood plasma osmolality; this leads to too little fluid excretion by the kidneys with the emergence of an insufficiently diluted urine); occurrence in cerebral hemorrhage, brain tumor, meningitis (meningitis), encephalitis (brain inflammation), tuberculosis, pneumonia (pneumonia), carcinoma
Cardiovascular system (I00-I99).
- Heart failure (cardiac insufficiency)
- Hypotension (low blood pressure)
Infectious and parasitic diseases (A00-B99).
- Diarrhea (diarrhea)
Liver, gallbladder, and biliary tract-pancreas (pancreas) (K70-K77; K80-K87).
- Liver cirrhosis (irreversible damage to the liver associated with marked remodeling of liver tissue) with ascites (abdominal dropsy).
- Pancreatitis (inflammation of the pancreas).
Mouth, esophagus (esophagus), stomach, and intestines (K00-K67; K90-K93).
- Ileus (intestinal obstruction)
- Peritonitis (inflammation of the peritoneum)
Psyche – nervous system (F00-F99; G00-G99)
- Bulimia nervosa (binge eating disorder).
- Meningitis (meningitis)
- Cerebral salt wasting syndrome
Symptoms and abnormal clinical and laboratory findings not elsewhere classified (R00-R99).
- Vomiting
- Diarrhea (diarrhea)
- Polydipsia (excessive thirst)
Genitourinary system (kidneys, urinary tract – reproductive organs) (N00-N99)
- Chronic renal failure (slowly progressive reduction in renal function).
- Nephrotic syndrome – collective term for symptoms that occur in various diseases of the glomerulus (renal corpuscles); the symptoms are proteinuria (increased excretion of protein in the urine) with a loss of protein; hypoproteinemia, peripheral edema (water retention) due to hypoalbuminemia (decreased level of albumin in the blood), hyperlipoproteinemia (lipid metabolism disorder).
- Salt loss kidney
Injuries, poisonings and other consequences of external causes (S00-T98).
- Muscle trauma
- Burns
Operations
Other causes
- Iatrogenic (hypotonic solutions, dialysis, parenteral therapy).
- Increased fluid intake (water intoxication).
Medication
- ACE inhibitor4
- Analgesics
- Nonsteroidal anti-inflammatory drugs (NSAIDs)3, also called nonsteroidal anti-inflammatory drugs (NSAPs) or NSAIDs.
- Antidepressants
- Group of noradrenergic and specific serotonergic antidepressants (NaSSA) – mirtazapine [moderate risk].
- Selective serotonin–norepinephrine reuptake inhibitor (SSNRI) – venlafaxine [high risk].
- Selective serotonin reuptake inhibitors1 (SSRI = Selective Serotonin Reuptake Inhibitor) – citalopram, escitalopram, fluvoxamine, fluoxetine, paroxetine, sertarline [high risk].
- Tricyclic antidepressants (TCAs) – amitriptyline4 [moderate risk]
- Anticonvulsants (carbamazepine1, gabapentin, lamotrigine, topiramate).
- Antimalarials (atovaquone).
- Antipsychotics (neuroleptics) – haloperidol4
- Diuretics
- Thiazide diuretics (hydrochlorothiazide (HCT), benzthiazide, clopamide, chlortalidone (CTDN), chlorothiazide, hydroflumethiazide, indapamide, methyclothiazide, metolazone, polythiazide and trichloromethiazide, xipamide).
- Drugs
- Ecstasy4
- Opiates1
- Fibrates (Clofibrate
- Filling/swelling agents (psyllium, flaxseed) [for prolonged use].
- Hormones
- Desmopressin2
- Oxytocin2
- Vasopressin2
- Infusions
- Physiological hypotonic solutions
- Glucose-containing liquids
- Sulfonylurea (glibenclamide glibenclamide, glibornuride, gliclazide, glipizide, gliquidone, glisoxepide, glycodiazine (Redul) third generation sulfonylureas: glimepiride (Amaryl) )
- Cytostatic drugs3 (cyclophosphamide, platinum compounds, vinca alkaloids).
1 Drugs that stimulate the release of antidiuretic hormone (ADH) 2 Drugs that exogenously supply ADH 3 Drugs that may potentiate the action of ADH 4 Drugs that may cause hyponatremia of unclear etiology.