Which of the following hormones is not involved in carbohydrate metabolism?

Melatonin is primarily known for its role in regulating sleep-wake cycles and does not have a significant impact on carbohydrate metabolism. 

Insulin promotes the uptake of glucose by cells, especially muscle and adipose tissue, and its conversion into glycogen. Glucagon stimulates the breakdown of glycogen into glucose (glycogenolysis) and synthesis of glucose from non-carbohydrate sources (gluconeogenesis). Epinephrine increases the breakdown of glycogen into glucose (glycogenolysis), releasing it into the bloodstream. Cortisol promotes gluconeogenesis (the synthesis of glucose from non-carbohydrate sources like amino acids and glycerol).