Why do patients with hypothyroidism often gain weight?

Patients with hypothyroidism often experience weight gain primarily due to a decrease in metabolism. The thyroid hormones, particularly thyroxine (T4) and triiodothyronine (T3), play a crucial role in regulating the body's metabolic rate. When the thyroid gland is underactive and does not produce enough of these hormones, the body's ability to convert food into energy slows down significantly. This reduced metabolic rate means that the body burns fewer calories, leading to weight gain if caloric intake remains unchanged.

While other factors such as increased appetite, fluid retention, and hormonal imbalances can contribute to weight changes, the key factor in hypothyroidism-related weight gain is the decreased metabolism. This results in an energy surplus where the body stores excess calories as fat rather than utilizing them efficiently. Thus, understanding the link between thyroid function and metabolism is essential for managing weight in patients with hypothyroidism.