The study of glands is called?

Endocrinology is the study of glands and the hormones they produce. Glands are organs that release hormones to regulate many body functions like growth, metabolism, and reproduction.

Other options:
- Cardiology is the study of the heart.
- Entomology is the study of insects.
- None of these is incorrect because the correct term is endocrinology.

So, the correct answer is endocrinology.