Why hypothyroidism causes euvolemic hypnatremia?

Why hypothyroidism causes euvolemic hypnatremia?

Hypothyroidism, a condition characterized by an underactive thyroid gland, can lead to a variety of physiological changes in the body, including the development of euvolemic hypnatremia. Here’s an explanation of how hypothyroidism can cause this condition:

Decreased Water Excretion: One of the effects of hypothyroidism is a decrease in the production and release of thyroid hormones. Thyroid hormones play a crucial role in regulating various body functions, including the balance of water and electrolytes. In hypothyroidism, the reduced levels of thyroid hormones can result in decreased renal blood flow and reduced glomerular filtration rate (GFR). This leads to impaired water excretion by the kidneys.

Impaired Free Water Clearance: In individuals with hypothyroidism, the impaired renal function affects the ability of the kidneys to concentrate urine and excrete free water. Free water refers to water without solutes, and its clearance is important for maintaining the body’s water-electrolyte balance. In hypothyroidism, impaired free water clearance results in the inability to excrete excess water, leading to dilutional hyponatremia.

Increased Antidiuretic Hormone (ADH) Secretion: Another contributing factor to euvolemic hypnatremia in hypothyroidism is the increased secretion of antidiuretic hormone (ADH) by the pituitary gland. ADH promotes water reabsorption by the kidneys, reducing urine output and further exacerbating the retention of water and dilution of sodium levels.

Overall, in hypothyroidism, the combination of reduced renal function, impaired free water clearance, and increased ADH secretion leads to the development of euvolemic hypnatremia. Euvolemic refers to a normal fluid volume status, meaning there is no significant loss or gain of fluid from the body.

It’s important to note that euvolemic hypnatremia can have other causes as well, and proper evaluation by a healthcare professional is necessary to diagnose and manage the condition appropriately.