What is the effect of thyroid hormones on metabolic rate?

Thyroid hormones, primarily thyroxine (T4) and triiodothyronine (T3), are crucial regulators of metabolic processes in the body. Specifically, they are known to increase the metabolic rate by influencing the rate at which the body uses energy. These hormones enhance cellular oxygen consumption and promote the catabolism of macronutrients such as carbohydrates, fats, and proteins, leading to increased heat production and energy expenditure.

The increase in metabolic rate occurs due to several mechanisms, including the upregulation of enzymes involved in metabolic pathways, stimulation of mitochondrial activity for ATP production, and enhancement of the basal metabolic rate (BMR) in various tissues, particularly in the heart, liver, and muscles.

By promoting a higher metabolic rate, thyroid hormones play a fundamental role in maintaining energy balance, thermoregulation, and overall health. An underactive thyroid, or hypothyroidism, would lead to a decreased metabolic rate, potentially resulting in weight gain and fatigue, whereas an overactive thyroid, or hyperthyroidism, can cause an increased metabolic rate, leading to weight loss and restlessness.

Understanding the significant role thyroid hormones play in metabolic rate is essential for assessing conditions related to thyroid dysfunction and their systemic effects on the body.