Detailed answer

Hypothyroidism, a condition where the thyroid gland doesn't produce enough thyroid hormone, can cause fluid retention and poor circulation. This can lead to the appearance of dark circles and under-eye bags. The lack of thyroid hormone can slow down the function of the lymphatic system, which normally helps to remove excess fluid from the body. As a result, fluid can accumulate in the under-eye area, causing puffiness and bags. Additionally, hypothyroidism can affect the production of collagen, a key protein responsible for maintaining the skin's structure and elasticity. Collagen deficiency can contribute to the thinning of the under-eye skin and the visibility of blood vessels, causing dark circles to appear more prominent. Treating the underlying hypothyroidism with medication may help alleviate these specific skin concerns.