Which body system is responsible for hormone production?

The endocrine system is the correct choice as it is specifically responsible for the production and regulation of hormones in the body. Hormones are chemical messengers that are secreted into the bloodstream by endocrine glands, such as the thyroid, adrenal glands, and pancreas, among others. These hormones play crucial roles in regulating various physiological processes, including metabolism, growth and development, tissue function, and mood.

In contrast, the nervous system primarily focuses on transmitting signals throughout the body to enable rapid communication between different parts of the body. While it does interact with hormones through mechanisms like the hypothalamus controlling the pituitary gland, it is not responsible for hormone production itself.

The respiratory system's main function is to facilitate the exchange of gases, specifically oxygen and carbon dioxide, and does not play a role in hormone synthesis.

The circulatory system, while essential for transporting hormones throughout the body, does not produce them. Its primary responsibility is to circulate blood, nutrients, gases, and waste products to and from cells.

Overall, the endocrine system stands out as the key system directly involved in the synthesis, secretion, and regulation of hormones.