What hormone is primarily responsible for promoting hyperglycemia?

The hormone primarily responsible for promoting hyperglycemia is growth hormone. Growth hormone, produced by the anterior pituitary gland, plays a critical role in metabolism and helps to increase blood glucose levels through several mechanisms. It does this by stimulating gluconeogenesis and glycogenolysis in the liver, which enhances the release of glucose into the bloodstream, thereby contributing to higher blood sugar levels.

In addition to its effects on glucose, growth hormone also promotes the utilization of fats for energy, sparing glucose for use by the brain and red blood cells. The overall outcome of growth hormone secretion during times of fasting or stress is an increase in circulating glucose levels, leading to hyperglycemia.

The other hormones listed, such as calcitonin, aldosterone, and renin, have different primary functions. Calcitonin mainly lowers blood calcium levels, aldosterone regulates sodium and potassium balance, and renin plays a key role in blood pressure regulation and fluid balance rather than directly influencing glucose metabolism.