Which of the following hormones is known to have a tropic effect?

Adrenocorticotropic hormone (ACTH) is considered a tropic hormone because it specifically targets the adrenal cortex, stimulating it to produce glucocorticoids, particularly cortisol. Tropic hormones are defined by their ability to regulate the activity of other endocrine glands, thereby exerting an influence on hormone secretion rather than having a direct effect on non-endocrine tissues.

Insulin primarily regulates glucose levels in the blood and has metabolic effects on tissues rather than acting as a tropic hormone. Testosterone is a steroid hormone that influences the development of male characteristics and reproductive functions but does not primarily act on another endocrine gland. Thyroxine, while important for metabolism and growth, is also not classified as a tropic hormone since its main functions are not dependent on signaling other endocrine glands to release other hormones.