Important metabolic effects of thyroxine is/are:
**Core Concept**
Thyroxine, a hormone produced by the thyroid gland, plays a crucial role in regulating metabolism. It influences various metabolic processes, including thermogenesis, glycogenolysis, and protein synthesis.
**Why the Correct Answer is Right**
Thyroxine exerts its effects by binding to thyroid hormone receptors in various tissues, including the liver, muscle, and adipose tissue. This binding activates the thyroid hormone receptor, which then regulates the expression of genes involved in metabolism. Thyroxine increases the breakdown of glycogen to glucose (glycogenolysis) and stimulates the synthesis of proteins. Additionally, it enhances thermogenesis, the process of heat production in the body, which is essential for maintaining body temperature.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because, while thyroxine does have an effect on protein synthesis, it is not the primary metabolic effect of this hormone.
**Option B:** This option is incorrect because, although thyroxine does influence glucose metabolism, its primary effect is not on glucose uptake by cells.
**Option C:** This option is incorrect because, while thyroxine does have some effects on lipid metabolism, its primary metabolic effects are not related to lipid breakdown or synthesis.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that the metabolic effects of thyroxine are often seen in patients with hyperthyroidism, where an excess of thyroxine leads to an increased metabolic rate, weight loss, and other symptoms. Conversely, hypothyroidism, characterized by a deficiency of thyroxine, leads to a decreased metabolic rate, weight gain, and other symptoms.
**Correct Answer: D. All of the above.**