Myxedema is a potentially deadly endocrine regulation disease that usually arises in connection with pre-existing hypothyroidism, when the normal homeostatic mechanisms for responding to hypothyroidism are overwhelmed. It occurs most often in elderly women, and is usually characterized by swelling of the skin and other soft tissues (Wall, 2000). The thyroid gland is central to homeostatic metabolic functions, and operates as part of a complex feedback loop involving both the pituitary and hypothalamus to control essential elements of fluid and electrolyte balance and thermoregulation. Under normal conditions, the hypothalamus influences pituitary hormonal output of thyroid stimulating hormone (TSH) via the secretion of thyrotropin releasing hormone (TRH). Virtually any disruption of the precise functioning of these individual glands, or their complex interrelationships can precipitate conditions of hyperthyroidism and Grave's Disease or hypothyroidism and myxedema (MedicineNet, 2002).

Classic symptoms of myxedema include facial puffiness caused by subcutaneous accumulation of mucoploysaccharide, coarsening or roughening facial features and excess facial hirsutism, which often give patients a much older appearance -- sometimes by two decades -- than their chronological age. Other symptoms include a decline of mental processes and functioning, as well as impaired muscle stretch and relaxation reflexes. Since unexplained hoarseness sometimes occurs in conjunction with hypothyroidism, physicians must also be cautious about misdiagnosing the cause as a function of ordinary laryngeal diseases (Schneiderman, 1993).

While more often related to chronic hypothyroidism, myxedema onset is sometimes much more sudden. In its most extreme manifestations, myxedema affects multiple organ systems, causing hypothermia (lowering the core body temperature by three degrees...

Partly for this reason, mortality rates, (which are 100% without treatment) may still approach 50% even with early diagnosis and aggressive intervention (Manifold, 2001).
Causes and Frequency:

By far, the most common cause of myxedema and thyroid deficiency is either primary hypothyroidism resulting from loss or atrophy of thyroid tissue, secondary hypothyroidism, resulting from hypothalamic or pituitary malfunction, or goitrous hypothyroidism, resulting from direct impingement from enlarged goitrous tissue.

Surgical removal (or radiological destruction) of hypothalamic or pituitary tissues is also an obvious cause of myxedema and myxedema coma in the absence of chronic hypothyroidism (Wall, 2000).

Iodine deficiency-based endemic goiter is also implicated as a causal factor of myxedema, which is corroborated by surveys of iodine-deficient areas, such as the mountainous regions of the Andes and Himalayas where glacier activity may leach iodine from the soil. Worldwide, evidence derived primarily from neonatal screening programs suggests that myxedema affects as many as 200 million people and as many as one in every four thousand births. In the United States, myxedema affects women approximately five to ten times as frequently as it affects men, with 2% of adult women exhibiting symptoms of hypothyroid malfunction (Manifold, 2001).

Hyperthyroidism and myxedema are closely related to other metabolic diseases resulting from thyroid malfunction such as Grave's Disease, even though the latter is a function of hyperthyroidism in which too much, rather than too little thyroid hormone is produced. The two main thyroid hormones are thyroxine…