The secretion of insulin normally inhibits secretion of which of the following hormones?

Insulin plays a crucial role in regulating blood glucose levels and has various effects on hormone secretion in the body. One of its key functions is to inhibit the secretion of glucagon. Glucagon is a hormone produced by the alpha cells of the pancreas and is responsible for increasing blood glucose levels by promoting gluconeogenesis and glycogenolysis in the liver.

When insulin is secreted following a meal when blood glucose levels are elevated, it acts to lower those levels by facilitating the uptake of glucose into cells and also suppresses the secretion of glucagon. This suppression is vital for ensuring that blood glucose levels do not rise too high, as glucagon would otherwise promote additional release of glucose into the bloodstream, counteracting the effects of insulin. Understanding this feedback mechanism is essential for managing conditions like diabetes, where insulin regulation is often disrupted.

In contrast, cortisol, adrenaline, and thyroid hormone are not directly inhibited by insulin in the same manner, as their regulatory pathways are more complex and involve different mechanisms influenced by stress, metabolic demands, and circadian rhythms, rather than directly opposing the action of insulin.