Which hormone is naturally produced by the body and classified as a steroid?

Testosterone is the hormone classified as a steroid and is produced naturally by the body. Steroid hormones are derived from cholesterol and include substances that regulate various physiological functions within the body. Testosterone, specifically, is key in the development of male reproductive tissues and the promotion of secondary sexual characteristics such as increased muscle and bone mass.

Cortisol, while also a steroid hormone and produced by the adrenal glands, is not the only correct option here. It plays a crucial role in metabolism, immune response regulation, and stress response, contributing to the body's ability to manage stress and inflammation.

While insulin is a peptide hormone and adrenaline is a catecholamine, neither are classified as steroid hormones. Therefore, focusing on testosterone provides a clear example of a natural steroid hormone produced by the body, with significant implications in both male and female physiology.