Which statement correctly differentiates tropic hormones from direct effector hormones?

Which statement correctly differentiates tropic hormones from direct effector hormones?

• A. They both act directly on peripheral tissue.
• B. They both act directly on another endocrine gland.
• C. Tropic hormones act on peripheral tissue while direct effector hormones act on endocrine glands.
• D. Tropic hormones act on endocrine glands while direct effector hormones act on peripheral tissues.

Answer: (D)

Tropic hormones are signals that regulate other endocrine glands, telling them to release or suppress their own hormones. Direct effector hormones, on the other hand, act directly on peripheral (non-endocrine) tissues to produce a physiological response. This distinction is what sets the two apart: tropic hormones target endocrine glands, while direct effector hormones target tissues outside of the glands. For example, tropic hormones like TSH stimulate the thyroid to release T3 and T4, and ACTH stimulates the adrenal cortex to secrete cortisol. Direct effector hormones like insulin act on liver, muscle, and adipose tissue to control glucose metabolism, and antidiuretic hormone acts on the kidneys to regulate water reabsorption. Therefore, the best description is that tropic hormones act on endocrine glands while direct effector hormones act on peripheral tissues.

Tropic hormones are signals that regulate other endocrine glands, telling them to release or suppress their own hormones. Direct effector hormones, on the other hand, act directly on peripheral (non-endocrine) tissues to produce a physiological response.

This distinction is what sets the two apart: tropic hormones target endocrine glands, while direct effector hormones target tissues outside of the glands. For example, tropic hormones like TSH stimulate the thyroid to release T3 and T4, and ACTH stimulates the adrenal cortex to secrete cortisol. Direct effector hormones like insulin act on liver, muscle, and adipose tissue to control glucose metabolism, and antidiuretic hormone acts on the kidneys to regulate water reabsorption.

Therefore, the best description is that tropic hormones act on endocrine glands while direct effector hormones act on peripheral tissues.