Myxedema Is a Potentially Deadly Endocrine Regulation

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 or more), diastolic hypertension, resparatory dysfunction and sleep apnea, ultimately developing into myxedema coma, which is only treatable through near-toxic doses of thyroxin. 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 (T-4), and triiodothyronine (T-

3), and while T-4 constitutes 99.9% of production, T-3, which constitutes only 0.1% is associated with the most metabolic control and biological activity (MedicineNet.com, 2002). Since hypothyroidism, and particularly myxedema coma, are treated with extreme doses of thyroid hormone, Graves Disease is a possible complication of advanced hypothyroidism and the therapeutic intervention of myxedema.

Diagnosis:

In the context of the disease, coma has a different meaning than its usual connotation, since myxedema coma rarely includes any loss of consciousness, and is far more readily (and often) diagnosed by progressive mental decline in the absence of other causes (Wall, 2000). Luckily, myxedema only progresses to the point of myxedema coma in approximately one out of every thousand cases of hypothyroidism (Manifold, 2001). Since the most likely precipitating factors for the progression of hypothyroidism into myxedema coma include infection such as pneumonia and urosepsis, blood and urine cultures along with chest X-rays are required, and one school of thought also recommends broad spectrum antibiotic administration concurrent with initial treatment of myxedema (Wall, 2000).

Early diagnosis of myxedema coma is crucial to effective treatment with immediate hospitalization, very high doses of thyroid hormone, hydrocortisone and other appropriate intensive treatment, so physicians are trained to prescribe diagnostic testing whenever geriatric female patients present with symptoms of mental decline, particularly when those symptoms first manifest themselves during the winter months.

Likewise, hypothyroidism must be considered whenever female patients especially those over the age of forty) experience fatigue, weight gain, constipation and complain of cold temperature intolerance (Wall, 2000). Since one of the primary indications of myxedema is mental function decline and facial tissue swelling, its symptoms are sometimes overlooked or misdiagnosed as other psychological or psychosocial issues, including chronic alcoholism (Schneiderman, 1993).