Myxedema Coma

Decompensated hypothyroidism: A review for the emergency clinician

BACKGROUND

Decompensated hypothyroidism, formerly known as myxedema coma, is an endocrine emergency that commonly presents with altered mental status, as well as hypothermia and depressed vital signs. The condition is often caused by an inciting event, which may lead to significant delays in the diagnosis and management of this disease. Although the incidence is low, this disease is associated with significant morbidity and mortality. Therefore, it is important for emergency clinicians to be aware of this condition.

OBJECTIVE

This narrative review evaluates the emergency medicine diagnosis and management of adult patients with decompensated hypothyroidism.

DISCUSSION

Decompensated hypothyroidism is a severe hypothyroid state associated with multiple organ failure. The diagnosis can be challenging due to similarities with more common diseases and lack of consideration of the diagnosis. Many patients may present with altered sensorium or depressed vital signs. Clinicians should obtain a thyroid stimulating hormone and free thyroxine level when considering the diagnosis. Management involves resuscitation, early steroid supplementation, thyroid hormone replacement, and treatment of the inciting event.

CONCLUSIONS

Decompensated hypothyroidism should be considered in the evaluation of patients with altered sensorium and depressed vital signs so as to not miss this critical diagnosis.

Thyroid disease and the nervous system

Thyroid disorders are common in the general population and in hospitalized patients. Thyroid disease may present first with neurological complications or else may occur concurrently in patients suffering other neurological disorders, particularly those with an autoimmune etiology. For this reason neurologists will commonly encounter patients with thyroid disease. This chapter provides an overview of the neurological complications and associations of disorders of the thyroid gland. Particular emphasis is placed on conditions such as thyrotoxic periodic paralysis and myxedema coma in which the underlying thyroid disorder may be occult leading to a first, often emergency, presentation to a neurologist. Information about clinical features, diagnosis, pathogenesis, therapy, and prognosis is provided. Emphasis is placed on those aspects most likely to be relevant to the practicing neurologist and the interested reader is directed to references to good, recent review articles for further information.

Endocrinologic and metabolic complications in the intensive care unit

Critical illness provides major stresses on all body systems, including those serving important regulatory functions. Endocrinologic and metabolic abnormalities are common on presentation and during hospitalization in the intensive care unit. Some of these abnormalities are the focus of this article. The authors review abnormalities of the adrenal and thyroid glands and in the metabolism of glucose, and include a brief review of abnormalities of sodium and calcium metabolism.

Relationship of admission thyroid function tests to outcome in critical illness

One hundred and eighty patients had serum thyrotropin, total triiodothyronine and free thyroxine concentrations measured within 3 h of admission to the Intensive Therapy Unit to assess whether thyroid function tests could predict outcome in critical illness. Overall mortality was 30.6%. Nonsurvivors were older (p = 0.001), and had higher APACHE II scores (p < 0.001) and predicted mortalities (p < 0.001). There was no difference in the median values of thyrotropin, total triiodothyronine and free thyroxine concentrations between survivors and nonsurvivors. Thyrotropin concentration was subnormal in 15 patients, normal in 152 and elevated in 13 patients. In contrast, 80 patients had subnormal triiodothyronine concentration. Free thyroxine was subnormal in five patients. Thyrotropin, total triiodothyronine and free thyroxine concentrations were not related to outcome (p = 0.360, p = 0.622, p = 0.726, respectively). No variable independently predicted death. Total triiodothyronine concentrations were lower in patients who received dopamine before admission to the intensive therapy unit than those who did not (p = 0.008); thyrotropin and free thyroxine concentrations were not influenced by dopamine administration. Serum concentrations of thyrotropin, total triiodothyronine and free thyroxine measured within 3 h of admission to the intensive therapy unit are not predictive of outcome.

Neurologic complications of thyroid and parathyroid disease

Common thyroid and parathyroid disorders present with reversible neurologic signs and symptoms affecting the central and peripheral nervous system, musculature, and mental function. Patients with thyrotoxicosis may have myopathy, spasticity, seizures, and multiple psychiatric symptoms. A deficiency of thyroid hormone also causes muscle weakness and may be accompanied by reversible muscle hypertrophy or movement disorders. The chronic hypercalcemia that develops secondary to hyperparathyroidism produces many psychiatric and cognitive symptoms, as well as a reversible myopathy. Calcium deficiency leads to neuromuscular irritability, paresthesias, and tetany. Psychiatric disorders are also common in this disorder.

Hormones and epilepsy through the lifetime

Hormones influence brain function from gestation throughout life and may affect the seizure threshold by altering neuronal excitability. Estrogen enhances and progesterone diminishes neuronal excitability experimentally, whereas testosterone and corticosteroids have less consistent effects. Hormonal effects in the CNS also depend on the region of brain in which the hormone acts. Sites of action for most steroid hormones include the hypothalamus and limbic cortex, providing a mechanism for modulating behavior and endocrine function. Seizure patterns may change at certain life stages, perhaps as a result of alterations in hormones. At puberty, epilepsy and benign rolandic epilepsy often remit, while juvenile myoclonic and photosensitive epilepsy may arise. Other types of epilepsy do not respond predictably to events in the reproductive life or to advancing age. In some women, fluctuations in hormones over the menstrual cycle appear to increase seizure vulnerability, probably reflecting changes in relative amounts of estrogen and progesterone. Seizure patterns can be altered, for better or worse, during pregnancy. Whether this reflects the effects of hormones or changes in levels of antiepileptic drugs is not resolved. More information is needed about changes in established epilepsy at menopause and in the elderly. Better understanding of endocrine effects on seizures over a lifetime should lead to more effective epilepsy therapies.