[The thyroid gland, the parathyroid gland and the skin]

Hormones of the thyroid gland (thyroxine, tri-iodothyronine) control the metabolism of cells and tissue of the body, while parathormone and calcitonine are balancing the intra- and extracellular levels of calcium and phosphorus by governing some metabolic functions of bones, kidney and small intestine. Growth, maturation and metabolic homeostasis of the organism depend, among other intrinsic factors, on a normal production and secretory rate of both thyroidal and parathyroidal hormones. Clinical conditions of hyperthyroidism induce 1. increased metabolic turnover of the body with transcutaneous heat loss, 2. disordered growth of hairs and nails, 3. hyperpigmentation of skin, 4. pruritus with or without urticaria. Pretibial (usually symmetrical) myxedema may be associated with conditions of either hyper- or hypothyroidism (e.g., Hashimoto's thyroiditis); if combined with bilateral exophthalmus and acropachyderma of fingers and toes, it is called Diamond syndrome, or E.M.O. syndrome. In hypothyroidism, the skin feels chilly and dry, looks pale, and may present follicular keratoses with or without secondary eczema. The hair appears dull and sparse due to disordered anagen phase. Skin wounds heal with delay. Diffuse myxedema originates in the papillary and periadnexal connective tissue and eventually extends to the dermis as a whole. Clinical conditions of hyperparathyroidism rarely cause secondary calcification of the skin; they may induce severe pruritus, particularly in secondary hyperparathyroidism due to renal failure. Impetigo herpetiformis or generalized pustular psoriasis, resp., may be set off by excessive surgical removal of the goiter. Congenital maldevelopment of both thymus and parathyroid gland leads to cellular immune deficiency with secondary chronic muco-cutaneous candidosis.