Which system is comprised of specialized, ductless glands that regulate hormone production?

The Endocrine System is indeed comprised of specialized, ductless glands that produce and secrete hormones directly into the bloodstream. These hormones act as chemical messengers that regulate a wide array of physiological processes in the body, including metabolism, growth, development, tissue function, and mood. Glands such as the pituitary, thyroid, adrenal, and pancreas are all part of this system, each playing a specific role in regulating bodily functions.

In contrast, the Nervous System primarily communicates through electrical signals and neurotransmitters, functioning through a complex network of neurons. It controls both voluntary movements and involuntary actions, but it does not secrete hormones.

The Reproductive System focuses on the organs involved in producing offspring and may interplay with hormonal signals from the endocrine system, but it does not encompass the entirety of hormone regulation across the body.

Similarly, the Digestive System handles the mechanical and chemical breakdown of food, the absorption of nutrients, and waste elimination, but it is not primarily involved in the regulation of hormone production.

Thus, the Endocrine System is distinctly defined by its role in hormone regulation, making it the correct choice in this context.