Which of the following is NOT an example of an endocrine gland?

The sebaceous gland is not classified as an endocrine gland; it is considered an exocrine gland. The primary distinction between endocrine and exocrine glands lies in their methods of secretion. Endocrine glands secrete hormones directly into the bloodstream, where they travel to various target organs to exert their effects on different physiological processes.

In contrast, exocrine glands, such as the sebaceous gland, release their products through ducts to specific locations, usually onto surfaces such as the skin. Sebaceous glands secrete sebum, an oily substance that helps to lubricate and protect the skin and hair.

The pituitary gland, thyroid gland, and adrenal gland are all examples of endocrine glands. They are responsible for secreting various hormones that regulate vital bodily functions, including metabolism, growth, and stress responses. By focusing on their secretion methods, it's clear why the sebaceous gland is the outlier in this question.