The primary function of the hypothalamus in homeostasis is to regulate the body's internal environment. It maintains critical bodily functions such as temperature, hunger, thirst, and sleep-wake cycles. The hypothalamus serves as a command center, receiving information from various body systems and responding appropriately to maintain balance. For instance, if body temperature rises, the hypothalamus signals mechanisms like sweating to cool the body. Its role is essential for overall health and stability in physiological processes.