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Acquired Hypothyroidism

Contents
  1. Read book excerpt
  2. Autoimmune Hemolytic Anemia: Introduction
  3. Autoimmune Hemolytic Anemia Causes
  4. Autoimmune Hemolytic Anemia Complications
  5. Autoimmune Hemolytic Anemia Treatments
  6. Statistics
  7. Autoimmune Hemolytic Anemia Overview
  8. More book excerpts for Autoimmune Hemolytic Anemia

Acquired Hypothyroidism: Excerpt from The 5-Minute Pediatric Consult

Adda Grimberg, MD

Acquired Hypothyroidism - BASICS

Acquired Hypothyroidism - description

Hypothyroidism that occurs after the neonatal period

Acquired Hypothyroidism - epidemiology

Acquired Hypothyroidism - incidence

  • May develop at any age
  • Autoimmune thyroid disorders occur more frequently in children and adolescents with type 1 diabetes mellitus.

Acquired Hypothyroidism - prevalence

Chronic lymphocytic thyroiditis prevalence correlates with iodine intake; countries with the highest dietary iodine also have the highest prevalence.

Acquired Hypothyroidism - risk factors

Acquired Hypothyroidism - genetics

  • Family history of thyroid disease or other autoimmune endocrinopathies increases risk.
  • Genetic predisposition in patients with chronic lymphocytic thyroiditis; 30–40% of patients have a family history of thyroid disease, and up to 50% of their 1st-degree relatives have thyroid antibodies.
  • Weak associations of chronic lymphocytic thyroiditis with certain human leukocyte antigen haplotypes
  • Autoimmune thyroid disease may be part of Schmidt syndrome (type II polyglandular autoimmune disease).
  • Genetic syndromes associated with higher incidence of autoimmune thyroiditis:
    • Down syndrome
    • Turner syndrome (especially those with isochromosome Xq)

Acquired Hypothyroidism - etiology

  • Myriad causes (see “Differential Diagnosis”)
  • Can result from thyroid gland dysfunction (primary hypothyroidism) or from pituitary/hypothalamic dysfunction leading to understimulation of the thyroid gland (secondary and tertiary hypothyroidism)

Acquired Hypothyroidism - associated conditions

  • Vitiligo
  • Other autoimmune endocrinopathies
  • Pernicious anemia

Acquired Hypothyroidism - DIAGNOSIS

Acquired Hypothyroidism - signs & symptoms

  • Early primary hypothyroidism can be asymptomatic.
  • Hypothyroid-related symptoms indicate progression from compensated to uncompensated hypothyroidism.
  • Hypothyroidism may be preceded in some cases by temporary hyperthyroidism (Hashitoxicosis).
  • Goiter may be the presenting sign of acquired hypothyroidism; tenderness suggests an infectious process.

Acquired Hypothyroidism - history

  • Linear growth failure can be the 1st sign of thyroid dysfunction.
  • Declining school performance is a sensitive marker for lethargy and reduced focusing.
  • Radiation exposure, history of diabetes, family history of autoimmune disease

Acquired Hypothyroidism - physical exam

  • Bradycardia: Thyroid hormone has cardiac effects.
  • Short stature (or fall-off on growth curve) and increased upper/lower segment ratio: Euthyroidism is required to maintain normal growth.
  • Goiter: Note consistency, symmetry, nodularity, signs of inflammation:
    • May give a clue regarding cause of hypothyroidism
    • May provide a clinical marker to follow during therapy
  • Myxedema (water retention) is not limited to subcutaneous tissue; it may also lead to cardiac failure, pleural effusions, and coma.
  • Muscle hypertrophy, yet muscle weakness most obvious in arms, legs, and tongue; hypothyroidism causes disordered muscle function.
  • Delayed relaxation phase of deep tendon reflexes due to slowed muscle contraction
  • Pale, cool, dry, carotenemic skin due to decreased cell turnover
  • Increase in lanugo hair in children; can be reversed with treatment
  • Sexual development is an important factor.
  • Hypothyroidism can be associated with:
    • Delayed puberty (due to low thyroid hormone level)
    • Precocious puberty and galactorrhea (due to elevated TSH)

Acquired Hypothyroidism - tests

Acquired Hypothyroidism - lab

  • TFree TAntithyroglobulin and antimicrosomal (antiperoxidase) antibodies are markers for chronic lymphocytic thyroiditis.
  • The following conditions may test false-positive for acquired hypothyroidism:
    • Thyroid-binding globulin deficiency: Low total TPeripheral resistance to thyroid hormone: Normal/High total T“Euthyroid sick” syndrome: low T
    • The following tests may be affected in acquired hypothyroidism:
      • Serum creatinine: Elevated due to reduced glomerular filtration rate
      • LDL cholesterol level: Elevated due to decreased LDL receptor expression
      • Creatine kinase: Increased; hypothyroidism is a rare cause of rhabdomyolysis

    Acquired Hypothyroidism - imaging

    Head MRI for suspected secondary/tertiary hypothyroidism or pituitary or hypothalamic lesion

    Acquired Hypothyroidism - differencial diagnosis

    • Immunologic:
      • Chronic lymphocytic thyroiditis (Hashimoto thyroiditis)
      • Polyglandular autoimmune syndrome (Schmidt syndrome)
    • Infectious:
      • Postviral subacute thyroiditis
      • Associated with congenital infections:
        • Rubella
        • Toxoplasmosis
    • Environmental:
      • Goitrogen ingestion:
        • Iodides
        • Expectorants
        • Thioureas
    • Iatrogenic:
      • Following surgical thyroidectomy for thyroid cancer, hyperthyroidism, or extensive neck tumors
      • Following radioiodine ablative therapy for hyperthyroidism or thyroid cancer
      • Following irradiation to the head or neck for cancer treatment
      • Medications: lithium, amiodarone, iodine contrast dyes, tiratricol (an OTC fat-loss supplement)
    • Metabolic:
      • Cystinosis
      • Histiocytosis X
    • Congenital:
      • Late-onset congenital-large ectopic gland
    • Genetic syndromes:
      • Down syndrome
      • Turner syndrome
      • Secondary or tertiary hypothyroidism
      • Hypothalamic or pituitary disease
    • Consumptive hypothyroidism:
      • Due to increased type 3 iodothyronine deiodinase activity in hemangiomas

    Acquired Hypothyroidism - TREATMENT

    Acquired Hypothyroidism - medication

    L-Thyroxine (synthetic thyroid hormone) replacement

    • Indicated for the treatment of overt or compensated hypothyroidism
    • 2–5 mcg/kg/d PO, once daily
    • Monitor TDuration of therapy:
      • Lifetime
      • In 30% of the cases, children with chronic lymphocytic thyroiditis will undergo spontaneous remission.
      • Need for treatment can be reassessed after growth is completed.

    Acquired Hypothyroidism - FOLLOW UP

    Acquired Hypothyroidism - prognosis

    • If patients are compliant, prognosis is excellent.
    • Treated patients often resume growth at a rate greater than normal (catch-up growth).
    • In children in whom treatment has been delayed, catch-up growth may not fully normalize height to predicted values.
    • Other signs and symptoms resolve at a variable rate.
    • Goiters in chronic lymphocytic thyroiditis may not completely regress with treatment (enlargement due to persistent inflammation does not correct, though TSH-mediated hypertrophy will).

    Acquired Hypothyroidism - complications

    • Most significant complication is impaired linear growth.
    • Puberty can also be affected.
    • Myxedema coma may occur.
    • Encephalopathy of varied clinical presentation has been associated with high titers of thyroid antibodies, especially antimicrosomal; responds well to corticosteroid treatment.

    Acquired Hypothyroidism - patient monitoring

 
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