Why does hemoglobin decrease in hyperthyroidism?

In hyperthyroidism, the increased levels of thyroid hormones can have several effects on the body, including alterations in hemoglobin levels. Hemoglobin is the oxygen-carrying protein in red blood cells, and its decrease in hyperthyroidism can be attributed to several factors:

Increased Red Blood Cell Destruction: Thyroid hormones stimulate the bone marrow to produce more red blood cells, leading to an increase in their turnover. This increased turnover results in the premature destruction of red blood cells, resulting in a decrease in hemoglobin levels.

Impaired Iron Utilization: Thyroid hormones can interfere with the absorption and utilization of iron, which is essential for the production of hemoglobin. This impaired iron utilization can contribute to the development of iron-deficiency anemia and further decrease hemoglobin levels.

Altered Erythropoietin Production: Erythropoietin is a hormone produced by the kidneys that stimulates the bone marrow to produce red blood cells. In hyperthyroidism, the increased thyroid hormone levels can suppress the production of erythropoietin, resulting in a decreased production of red blood cells and lower hemoglobin levels.

Reduced Red Blood Cell Survival: The excessive levels of thyroid hormones can shorten the lifespan of red blood cells, leading to their premature destruction and decreased hemoglobin levels.

It is important to note that not all individuals with hyperthyroidism experience decreased hemoglobin levels. Some may have normal hemoglobin levels, while others may develop anemia due to the various factors mentioned above. Therefore, regular monitoring of hemoglobin levels and assessment of iron status are crucial in managing patients with hyperthyroidism.