Which external factor is NOT known to affect hormone secretion?

Diet does play a significant role in hormone regulation and secretion. Various nutrients and dietary patterns can influence the levels of hormones in the body. For example, carbohydrates can affect insulin secretion, while protein intake can influence levels of hormones like glucagon and growth hormone.

In contrast, stress, sunlight, and chemicals are external factors that have well-documented effects on hormone secretion. Stress can trigger the release of cortisol and adrenaline from the adrenal glands. Sunlight, particularly exposure to light, influences the secretion of melatonin from the pineal gland, which regulates sleep-wake cycles and other hormonal processes. Similarly, various chemicals, including endocrine disruptors, can interfere with hormone signaling and secretion by mimicking or blocking the actions of natural hormones.

Thus, understanding the influence of various external factors like stress, sunlight, and chemicals helps provide clarity on their significant role in hormonal regulation, while diet is an essential and well-established contributor to hormone secretion.