Comprehensive Diabetes and Thyroid Disorders Practice Test 2026 - Free Pathophysiology, Symptoms, and Management Practice Questions and Study Guide

Thyroid hormones raise metabolic rate by driving cells to burn fuel more rapidly. T3 and T4 boost the expression of enzymes involved in glycolysis, the TCA cycle, and oxidative phosphorylation, and they increase mitochondrial number and activity. They also raise Na+/K+ ATPase activity, which uses energy constantly. This combination pushes resting energy use higher across most tissues. A key result is more heat produced—thermogenesis—partly through upregulation of thermogenic pathways in brown adipose tissue. As a result, basal metabolic rate goes up, heat production increases, and overall energy expenditure rises. That’s why thyroid hormone activity is associated with higher BMR, more heat generation, and greater energy use; contrasting choices that suggest decreases or no change don’t fit the hormone’s effect. In clinical terms, this explains why hyperthyroidism tends to cause weight loss and heat intolerance, while hypothyroidism causes weight gain and cold intolerance.