Beyond the Basics: Endocrine Emergencies

CEU Review Form Endocrine Emergencies Part 2 (PDF)Valid until January 2, 2008

This is the second part of a two-part series addressing endocrine emergencies involving the thyroid gland. Refer to Part One in the October issue and online at www.emsresponder.com to review the anatomy and physiology necessary to completely understand normal thyroid function and hypothyroidism.

As you may recall from last month's article, hyperthyroidism produces a hypermetabolic state from an excessive amount of circulating thyroid hormone, resulting in emergencies such as thyroid storm and thyrotoxic crisis. Key findings include agitation, weight loss, nervousness and palpitations. Hypothyroidism, on the other hand, occurs when the thyroid gland secretes an inadequate amount or no thyroid hormone. The effects are generally opposite those of hyperthyroidism. The lack of circulating thyroid hormone reduces the basal metabolic rate, often producing subtle clinical signs and symptoms that may progress over several years. If the hypothyroidism condition becomes extreme, it may result in a severe depression in the metabolic rate and produce a potentially life-threatening emergency called myxedema coma.

EPIDEMIOLOGY
     Hypothyroidism may produce a variety of signs and symptoms. Some patients may remain subclinical, showing no obvious signs of the disease process and not realizing they have the condition until their thyroid hormone and thyroid-stimulating hormone levels are tested. Still other patients may present with hypothermia, a decreased mental state and other overt clinical signs of the life-threatening condition of myxedema coma. It is most often the latter patient who accesses the EMS system seeking emergency care for a condition that is not well recognized by patients.

     In the United States, the incidence of hypothyroidism is 4.6-5.8%, with 3.6-4.3% remaining subclinical in both men and women. Those with overt signs and symptoms of hypothyroidism comprise approximately 0.3-2.2%, with a small number representing males. The incidence in females has been reported to be anywhere from 2 to 10 times higher than in males, which may reflect an increased prevalence of autoimmune thyroid disease found in females. Even though hypothyroidism can occur at any time, the incidence increases with age. Onset of the disease often occurs between 40 and 50 years of age, with a peak incidence in patients in their 70s. The disease is found most often in the Caucasian population followed by Latinos. Hypothyroidism may be found in the African-American population, but at a rate that is approximately three times less than that of Caucasians. Because hypothyroidism produces a decrease in metabolic rate and does not allow the proper use of calories for energy and heat production by the body, patients often cannot tolerate low ambient temperatures. Thus, the incidence of hypothyroidism and myxedema coma increases in the winter months.

PATHOPHYSIOLOGY
     Hypothyroidism is associated with failure of the thyroid gland, which may result from a lack of or decrease in stimulation of the thyroid gland by other hormones. The release of thyroid hormone occurs as a result of the secretion and circulation of a cascade of hormones from other endocrine glands. Failure of any one of these hormones may produce hypothyroidism. Thyrotropin-releasing hormone (TRH) is secreted from the hypothalamus and is responsible for triggering the release of thyroid-stimulating hormone (TSH) from the anterior pituitary gland. Thyroid-stimulating hormone stimulates the release of thyroid hormone (TH) from the thyroid gland. Thus, a failure in the release of either TRH from the hypothalamus or TSH from the anterior pituitary gland will result in an inadequate secretion of thyroid hormone.