When it comes to acne and the appearance of pimples, the endocrine gland that is most commonly linked is the reproductive gland (which includes the ovaries in females and testes in males). The hormones produced by these glands, particularly androgens, can increase oil production in the skin, leading to clogged pores and acne.
While the other glands (thymus, thyroid, pancreas) have important roles in the body, they are not directly responsible for the hormonal changes that typically lead to acne.