Hypothyroidism Disease

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

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.