What primarily affects sebaceous glands in the skin?

Sebaceous glands are primarily influenced by sex hormones, particularly androgens like testosterone. These hormones play a crucial role in regulating the size and activity of sebaceous glands, which in turn affects the production of sebum, the oily substance that helps keep the skin lubricated and protected. During puberty, for instance, there is an increase in androgen levels which leads to larger and more active sebaceous glands, often resulting in increased oiliness of the skin and, in some cases, acne.

While diet, environmental exposure, and age can have some impacts on skin health and gland function, their effects are secondary when compared to the direct hormonal regulation by sex hormones. Diet may influence overall skin condition and health, but it does not have the same direct impact on the sebaceous glands’ activity as sex hormones do. Environmental factors can affect how the skin looks and feels, but again, they don't directly control the gland's secretory function. Age can influence the number and efficacy of sebaceous glands, typically leading to a decrease in sebum production over time, but the immediate control of their activity primarily rests with hormonal changes throughout different life stages.