What is hypothyroidism?
Reduced thyroid function causing slowed cellular activities due to decreased thyroid hormone.
Where does primary hypothyroidism originate and what is TSH level?
In the thyroid with elevated TSH.
Where does central hypothyroidism originate and what is TSH level?
In the pituitary or hypothalamus with normal or decreased TSH.
Where does peripheral hypothyroidism originate and what is TSH level?
Extra-thyroidal with elevated TSH.
What complications can untreated hypothyroidism cause?
Cardiovascular, hematopoietic, metabolic, obstetric, fetal, neonatal, childhood complications, and myxedematous coma.
How does hypothyroidism prevalence change with age in adults?
It increases with age.
What is the worldwide prevalence range of hypothyroidism in adults?
Approximately 1–10%.
What is the prevalence of undiagnosed hypothyroidism in Europe?
Approximately 5%.
Which cause is most frequent for adult hypothyroidism?
Hashimoto thyroiditis.
What is the most frequent cause of hypothyroidism in iodine-deficient areas?
Iodine deficiency.
What is the approximate incidence of congenital hypothyroidism at birth?
1 in 3,000–4,000 births.
What is the incidence of central congenital hypothyroidism at birth?
1 in 50,000 births.
How does hypothyroidism affect metabolism and thyroid hormone availability?
It slows metabolism, reducing energy consumption and altering T4 and T3 availability.
What causes myxedema in terms of tissue infiltration?
Infiltration by extracellular matrix rich in acidic polysaccharides.
Why are thyroid hormones essential in children?
They are essential for bone growth and nervous-system development, especially brain growth.
What are the consequences of untreated hypothyroidism in children?
Disproportionate short stature, mental retardation, and cretinism.
Which symptoms does typical hypothyroidism cause related to energy and digestion?
Fatigue, cold intolerance, constipation, and weight gain despite reduced appetite.
What psychomotor and cardiac signs are typical in hypothyroidism?
Psychomotor slowing, delayed ideation, bradycardia, and delayed relaxation of deep tendon reflexes.
What symptoms result from myxedematous infiltration in hypothyroidism?
Dry skin, hoarseness, hearing loss, snoring, sleep apnea, myalgia, arthralgia, and carpal-tunnel paresthesia.
What characterizes subclinical hypothyroidism symptoms and hormone levels?
It is asymptomatic or mildly symptomatic with elevated TSH and normal peripheral thyroid hormones.
Which risks are linked to subclinical hypothyroidism in young patients with TSH >10 mIU/L?
Coronary disease, heart failure, dyslipidemia, and type 2 diabetes.
What percentage of pregnant women have overt hypothyroidism?
Approximately 0.5%.
Name one maternal complication of hypothyroidism during pregnancy.
Early miscarriage.
What is the consequence of untreated congenital hypothyroidism starting treatment after 3 months?
Irreversible neurological sequelae.
What developmental areas does untreated congenital hypothyroidism threaten?
Psychomotor and mental development.
Which causes can lead to adult primary hypothyroidism?
Iatrogenic, autoimmune, subacute, infiltrative, genetic, nutritional, or medication-related causes.
What are common acquired causes of central hypothyroidism?
Tumors, irradiation, surgery, trauma, infiltrative disease, or infection.
Which rare defects can cause central hypothyroidism?
Congenital and genetic defects affecting TRH, TSH, or combined pituitary function.
What percentage of permanent congenital primary hypothyroidism is due to thyroid dysgenesis?
70–80%.
What forms of thyroid dysgenesis cause congenital primary hypothyroidism?
Ectopia, athyreosis, hypoplasia, or hemiagenesis.
What is the first-line test for suspected primary hypothyroidism?
TSH measurement
How does TSH behave in overt and subclinical primary hypothyroidism?
It is elevated
What is the TSH level in central hypothyroidism?
Often inappropriately normal
What hormone measurement confirms central hypothyroidism?
Free T4
Which hormone test is unnecessary in assessing hypothyroidism?
Free T3
What cardiac conditions can hypothyroidism cause?
Myxedematous pericarditis, non-anginal chest pain, reversible systolic and diastolic dysfunction, and silent irreversible coronary atherosclerosis.
What triggers myxedematous coma in 95% of cases?
Cold exposure triggers myxedematous coma in 95% of cases.
What is the mortality rate of myxedematous coma?
Myxedematous coma causes death in 20% of cases.
How should levothyroxine replacement be taken daily?
Fasting 30–60 minutes before breakfast or at bedtime 2 hours after the last meal under consistent conditions.
What is the usual adult levothyroxine dosage and how does it change in pregnancy?
1.5–1.8 μg/kg/day normally, increasing by 30–50% during pregnancy.
How is levothyroxine treatment initiated in fragile or elderly patients?
Starting with 12.5–25 μg and increasing gradually with clinical, hormonal, and ECG monitoring.
How often is TSH reassessed during levothyroxine dose adjustment?
Every 6–8 weeks during adjustment and every 6–12 months when normal.
What monitoring is used in children on levothyroxine?
Monitoring includes growth and puberty with age-dependent dosing.
How does levothyroxine dosage vary with age in children?
From 10–15 μg/kg/day before 3 months to 1.6 μg/kg/day after 16 years.
What are treatment targets in congenital hypothyroidism?
Normal TSH and free T4 in primary disease; free T4 and free T3 in upper half of normal in central disease.
What is the most frequent congenital endocrinopathy?
Hypothyroidism.
What is the most frequent endocrine disease in adults?
Hypothyroidism.
What is the annual incidence rate of adult hypothyroidism?
0.5–1% per year.
When does the fetal thyroid begin to function during pregnancy?
From the 18th week of amenorrhea.
How do maternal thyroid hormones support early fetal development?
They cross the placenta in sufficient quantity for early development.
Which facial and skin signs are typical in hypothyroidism?
Puffy face, lateral eyebrow loss, macroglossia, periorbital edema, infiltrated pale-yellow skin, and erythrocyanotic cheekbones and lips.
What hair and nail changes occur in hypothyroidism?
Sparse hair, dry brittle hair, and ridged fragile nails.
What cardiovascular signs can hypothyroidism cause?
Diastolic hypertension from increased peripheral resistance or low blood pressure from reduced cardiac output, pleuropericardial effusion, and cardiomegaly.
Which endocrine and musculoskeletal symptoms are found in hypothyroidism?
Galactorrhea, myalgia, and arthralgia.
List two clinical features of myxedematous coma.
Hypothermia and bradycardia.
What serious risk is associated with myxedematous coma?
Risk of collapse.
What maternal factors can cause transient congenital hypothyroidism?
Maternal dysthyroidism or antibodies, iodine intoxication or deficiency, and maternal medications like antithyroid drugs and iodides.
What are the main causes of acquired childhood hypothyroidism?
Autoimmune, iodine-deficient, surgical, irradiation-related, medication-related, tumoral, traumatic, infiltrative, or infectious causes.
What do positive anti-thyroid peroxidase antibodies indicate?
Autoimmune thyroiditis
What does urinary iodine measurement help identify?
Iodine overload or deficiency
What is thyroglobulin a marker of?
Thyroid tissue
Which metabolic abnormalities are caused by hypothyroidism?
Dyscalcemia, increased bilirubin, increased muscle enzymes, hyperlipidemia, and dysglycemia.
What hematopoietic disorders can hypothyroidism cause?
Anemia, low protein S and C, and acquired von Willebrand disease with hemorrhage.
Which substances reduce levothyroxine absorption?
Meals, iron, calcium, magnesium salts, cholestyramine, aluminum hydroxide, sucralfate, and proton-pump inhibitors.
Answer 27 questions on Hypothyroidism.
1. What best defines hypothyroidism?
2. Which laboratory pattern most strongly suggests central hypothyroidism?
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