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What is the primary significance of hypothyroidism?
What is the primary significance of hypothyroidism?
What is the primary manifestation of fluid retention in hypothyroidism?
What is the primary manifestation of fluid retention in hypothyroidism?
Which of the following is a reversible cause of hypothyroidism?
Which of the following is a reversible cause of hypothyroidism?
Which of the following is a characteristic of the hair in patients with hypothyroidism?
Which of the following is a characteristic of the hair in patients with hypothyroidism?
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What is the primary mechanism by which lithium impairs thyroid hormone synthesis?
What is the primary mechanism by which lithium impairs thyroid hormone synthesis?
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What is the primary effect of thyroid hormones on the cardiovascular system?
What is the primary effect of thyroid hormones on the cardiovascular system?
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What is the expected result of serum TSH level in primary hypothyroidism?
What is the expected result of serum TSH level in primary hypothyroidism?
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What is the expected result of serum sodium concentration in hypothyroidism?
What is the expected result of serum sodium concentration in hypothyroidism?
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Which of the following is a common symptom of hypothyroidism?
Which of the following is a common symptom of hypothyroidism?
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What is the primary cause of myxedema in hypothyroidism?
What is the primary cause of myxedema in hypothyroidism?
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What is the expected result of serum prolactin concentration in primary hypothyroid disease?
What is the expected result of serum prolactin concentration in primary hypothyroid disease?
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What is the expected laboratory result in primary hypothalamic failure?
What is the expected laboratory result in primary hypothalamic failure?
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Which of the following is a secondary cause of hypothyroidism?
Which of the following is a secondary cause of hypothyroidism?
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What is the primary role of thyroid hormones in the central nervous system?
What is the primary role of thyroid hormones in the central nervous system?
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What is the expected result of titers of antibodies against thyroid gland proteins in Hashimoto thyroiditis?
What is the expected result of titers of antibodies against thyroid gland proteins in Hashimoto thyroiditis?
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Who should be screened for thyroid disease according to the American College of Physicians?
Who should be screened for thyroid disease according to the American College of Physicians?
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What is the primary characteristic of hypothyroidism disease?
What is the primary characteristic of hypothyroidism disease?
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Which of the following is the most common cause of hypothyroidism?
Which of the following is the most common cause of hypothyroidism?
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What is the trend in the prevalence of hypothyroidism with age?
What is the trend in the prevalence of hypothyroidism with age?
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What is the approximate prevalence of hypothyroidism in babies born in the United States?
What is the approximate prevalence of hypothyroidism in babies born in the United States?
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Which of the following is a characteristic of hypothyroidism in terms of gender?
Which of the following is a characteristic of hypothyroidism in terms of gender?
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What is the prevalence of hypothyroidism in women older than 60 years?
What is the prevalence of hypothyroidism in women older than 60 years?
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What is the primary effect of thyroid hormone deficiency on the body?
What is the primary effect of thyroid hormone deficiency on the body?
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What is the relative frequency of primary hypothyroidism compared to secondary hypothyroidism?
What is the relative frequency of primary hypothyroidism compared to secondary hypothyroidism?
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What would laboratory studies likely show in a case of hypothyroidism?
What would laboratory studies likely show in a case of hypothyroidism?
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What is the primary goal of therapy for hypothyroidism?
What is the primary goal of therapy for hypothyroidism?
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What is the treatment of choice for hypothyroid disease?
What is the treatment of choice for hypothyroid disease?
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What is the significance of the first 2 years of life in hypothyroid infants?
What is the significance of the first 2 years of life in hypothyroid infants?
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What is the mortality rate for myxedema coma?
What is the mortality rate for myxedema coma?
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What is the effect of inadequate treatment of hypothyroidism?
What is the effect of inadequate treatment of hypothyroidism?
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How long does it take to see significant increases in serum thyroxine levels after starting levothyroxine therapy?
How long does it take to see significant increases in serum thyroxine levels after starting levothyroxine therapy?
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What is the best time to take levothyroxine?
What is the best time to take levothyroxine?
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What is a common consequence of rapid replacement therapy with levothyroxine?
What is a common consequence of rapid replacement therapy with levothyroxine?
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What is the recommended frequency for increasing levothyroxine doses?
What is the recommended frequency for increasing levothyroxine doses?
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What is a potential consequence of chronic maintenance therapy with large doses of levothyroxine?
What is a potential consequence of chronic maintenance therapy with large doses of levothyroxine?
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What is the general outcome of patients who receive levothyroxine therapy?
What is the general outcome of patients who receive levothyroxine therapy?
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What is a common effect of myxedema coma on patients?
What is a common effect of myxedema coma on patients?
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What is the recommended daily dose of levothyroxine for most patients?
What is the recommended daily dose of levothyroxine for most patients?
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What can cause poor absorption of levothyroxine?
What can cause poor absorption of levothyroxine?
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What can interfere with the absorption of levothyroxine?
What can interfere with the absorption of levothyroxine?
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Study Notes
Hypothyroidism
- Hypothyroidism is a multi-symptom complex characterized by a deficiency of circulating triiodothyronine (T3) and thyroxine (T4)
- Thyroid hormone deficiency affects virtually all bodily functions, with severity related to the degree of hormone deficiency
Prevalence
- Hypothyroidism is more common in females than in males, with a prevalence 2 to 8 times higher in females
- Frequency of hypothyroidism increases with age, most prevalent in elderly populations
- In adults older than 60 years, hypothyroidism was reported in 5.9% of women and 2.4% of men
- Approximately 1 in 3,000-5,000 babies in the United States is born with hypothyroid disease
Clinical Manifestations
- Weakness, fatigue, intolerance to cold, constipation, weight gain, dry, flaky skin
- Weakness, joint pain, muscle pain, muscle cramps, headaches, menstrual abnormalities, thin and brittle nails, thinning of hair and eyebrows, slow speech and thought, pallor, low body temperature, hoarseness, decreased sense of hearing, taste, and smell, difficulty breathing, increased weight, enlarged thyroid gland, slow heart rate, lactation not associated with pregnancy
Causes and Risk Factors
- Primary hypothyroidism: Hashimoto thyroiditis, loss of viable thyroid gland tissue, external beam radiation, 131I therapy, bacterial or viral thyroiditis, congenital or acquired iodide deficiency, genetic thyroid enzyme defects, medications that impair thyroid hormone synthesis, foods that interfere with thyroid hormone synthesis
- Secondary hypothyroidism: deficient pituitary thyroid-stimulating hormone (TSH) secretion, deficient hypothalamic thyroid-releasing hormone (TRH) secretion, peripheral resistance to thyroid hormones
Pathophysiology
- Thyroid hormone affects many body tissues, regulating metabolic rate, body heat production, growth hormone secretion, skeletal growth, CNS development, β-adrenergic receptors, and Ca2-ATPase synthesis
- Maintenance of normal respiratory rate, muscle tone, and vigor
Diagnosis
- Based on patient history, physical examination, and laboratory thyroid function test results
- Laboratory tests may show: low or low-normal serum-free thyroxine concentration, low serum total thyroxine, high serum TSH level, low serum sodium concentration, high serum prolactin concentration, low hematocrit
Serious Complications and Prognosis
- Inadequate treatment leads to disease progression, worsening symptoms, and metabolic derangements
- Progressive hypothyroid disease may result in life-threatening myxedema coma, characterized by marked hypothermia, hypoventilation, and hypotension
- Mortality rate for myxedema coma is as high as 60%
Treatment
- Primary goal of therapy is to return patients to a normal thyroid (euthyroid) state
- Levothyroxine is the treatment of choice for hypothyroid disease, partially converted in the body to T3
- Doses can be increased by 25 µg every 1-3 weeks until the patient's thyroid status is normal
- Striking transformations in the patient's appearance, exercise tolerance, and mental state often occur within several days after initiating therapy
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Description
Hypothyroidism is a disease characterized by a deficiency of circulating thyroid hormones, affecting bodily functions and causing various symptoms. The severity of manifestations depends on the degree of hormone deficiency.
