Clinical diagnosis is readily possible when the typical aspects of the phenotype of hypothyroidism are present in the full manifestation of the syndrome (Sect. 7.1 ). Leading signs are, among others, a slowdown of physical and mental functions, fatigue, weight gain, cold intolerance, dry and pale skin, scrubby hair, bloated face, eyelid oedema, bradycardia and hyporeflexia. The diagnostic value of these symptoms lies more in their combined expression, because many of them are subtle or non-specific when viewed in isolation. The fully developed syndrome is however already often a sign of a long history of patient suffering. In extremis, a life-threatening exacerbation of myxedematous coma may occur, facilitated by an unrecognised disease and precipitated by other stressful events.