Which gland is not found on the lips or sex organs?

The thyroid gland is indeed not found on the lips or sex organs. It is an endocrine gland located in the neck, responsible for hormone production that regulates metabolism, growth, and development in the body. Unlike the apocrine and eccrine glands, which are associated with sweat and are located in various regions of the skin including those around the sex organs, the thyroid gland specifically functions to secrete hormones directly into the bloodstream rather than through ducts in the skin.

The apocrine and eccrine glands produce sweat, and while eccrine glands are widely distributed across the body, including the palms, soles, and forehead, apocrine glands are mainly found in areas like the armpits and the genital region. The pineal gland, which is also not located in the lips or sex organs, primarily functions to regulate sleep patterns through melatonin production, but it is primarily situated in the brain and is not directly related to skin or sweat production.

Thus, the thyroid gland stands out as the only gland in the list that does not have any relevance to the skin's surface in those specific areas.