However, the red-yellow pheomelanin is believed to cause the warm, golden, or auburn tones found in some types of brown hair. The range of colors produced by melanins is limited to shades of yellow, brown, red, and black. Grey hairs contain only a few melanin granules, spread out through the hair.
Hormones are your body's chemical messengers. They travel in your bloodstream to tissues or organs. Endocrine glands, which are special groups of cells, make hormones. The major endocrine glands are the pituitary, pineal, thymus, thyroid, adrenal glands, and pancreas. In addition, men produce hormones in their testes and women produce them in their ovaries.
Overview. The thyroid hormones affect nearly all tissues of the human body, including the skin. Skin tissues contain thyroid hormone receptors which, when occupied by thyroid hormones, stimulate cellular activity. Patients with hypothyroidism, or underactive thyroid disease, may experience skin symptoms that reflect diminished cellular skin activity in the absence of sufficient thyroid hormone. Some skin changes associated with hypothyroidism may cause itching.