Sebaceous glands, small oil producers in the skin, secrete sebum. Sebum lubricates and shields skin and hair from dehydration. Insufficient sebum production leads to dry, rough skin due to a deficit in moisture and lubrication. Sweat glands facilitate body cooling via sweat but do not lubricate the skin. Apocrine glands, a subtype of sweat glands primarily located in areas like the underarms, are associated with body odor. Thyroid glands, which regulate metabolism, are endocrine glands and do not produce skin oils. Consequently, a deficiency in lubrication from sebaceous glands results in dry skin.