What effect does thyroxine have on glucose levels?

What effect does thyroxine have on glucose levels?

• A. Decreased absorption from the GI tract
• B. No impact
• C. Increased absorption from the GI tract
• D. Decreases glycogen breakdown

Answer: (C)

Thyroxine, the major hormone produced by the thyroid gland, plays a significant role in metabolic processes, including the regulation of glucose levels. One of its effects is to increase the absorption of glucose from the gastrointestinal (GI) tract. This enhancement in glucose absorption occurs because thyroxine can stimulate the rate of digestion and increase the activity of enzymes involved in the breakdown of carbohydrates, ultimately allowing for more glucose to enter the bloodstream following a meal.

When circulating levels of thyroxine are elevated, there is an increase in overall metabolic rate, leading to greater energy demands which can further necessitate higher levels of glucose. This aligns with the role of thyroxine in promoting gluconeogenesis as well, helping to maintain blood glucose levels, especially during periods of fasting.

In contrast, the other options do not accurately reflect the known physiological effects of thyroxine on glucose metabolism. For example, the statement regarding decreased absorption does not align with thyroxine's stimulatory effects, and the assertion of no impact fails to recognize its clear role in glucose regulation. Moreover, the idea that it decreases glycogen breakdown contradicts that fact that thyroxine actually facilitates gluconeogenesis and glycogenolysis, contributing to an increase in blood glucose levels.