Graves Disease (GD)

smart doctor on

 Graves Disease (GD)     

Definition

  • Graves disease (GD) is an autoimmune disorder in which TSH receptor–stimulating autoantibodies (TRAb) bind to and activate TSH receptors on thyroid follicular cells.

  • This leads to increased thyroid hormone synthesis and release, causing hyperthyroidism and diffuse goiter.

  • It is the most common cause of hyperthyroidism in iodine-sufficient regions.more about hyperthyroidism

Epidemiology

  • Most common cause of hyperthyroidism in the United States and worldwide.

  • Female predominance: women are affected ∼10× more than men.

  • Typical age of onset: 20–50 years.

  • Family history: up to 50% of patients have a family history of autoimmune disease.

Etiology & Risk Factors

  • Genetic predisposition

    • Strong association with HLA-DR3 and HLA-B8.

  • Autoimmune basis

    • T- and B-cell–mediated loss of tolerance → production of stimulatory IgG against TSH receptor.

  • Environmental & triggering factors

    • Infectious agents (e.g., Yersinia enterocolitica, Borrelia burgdorferi).

    • Physical stress (surgery, trauma).

    • Psychological stress.

    • Pregnancy (especially postpartum, due to immune modulation).

Pathophysiology

  • General mechanism:

    • TRAb (IgG) bind TSH receptors → overstimulation of thyroid follicular cells → excess T3/T4 release → hyperthyroidism + diffuse goiter.

  • Graves ophthalmopathy (thyroid-associated orbitopathy, TAO):

    • Autoimmune lymphocyte infiltration of orbital fibroblasts.

    • Cytokine release (TNF-α, IFN-γ) → fibroblast activation → glycosaminoglycan (GAG) deposition + adipocyte proliferation.

    • Increased intraorbital fat and muscle volume → exophthalmos, lid retraction, diplopia.

  • Dermopathy (pretibial myxedema):

    • Fibroblast stimulation in dermis → GAG deposition → non-pitting pretibial edema, skin thickening.

  • Histology of thyroid in GD:

    • Tall, hyperplastic follicular cells.

    • Scalloped colloid (evidence of active resorption).

Clinical Features

General Symptoms (Hyperthyroidism)

  • Weight loss despite ↑ appetite.

  • Heat intolerance, sweating.

  • Palpitations, tachycardia.

  • Tremor, anxiety, irritability, insomnia.

  • Muscle weakness (proximal).

  • Frequent bowel movements/diarrhea.

Thyroid Enlargement

  • Diffuse, smooth, symmetrical goiter.

Ophthalmic Manifestations (Graves Ophthalmopathy)

  • Exophthalmos.

  • Lid retraction, lid lag (“thyroid stare”).

  • Conjunctival injection, chemosis.

  • Ocular motility disturbance → diplopia.

  • Corneal ulceration in severe cases.

Dermopathy

  • Pretibial myxedema: bilateral, non-pitting, waxy thickening of the skin.

Other Signs

  • Onycholysis (Plummer’s nails).

  • Restlessness, emotional lability.

Diagnosis

Thyroid Function Tests

  • TSH: suppressed (low or undetectable).

  • Free T4 and/or T3: elevated.

Autoantibodies

  • TRAb (TSH receptor antibodies): elevated, specific for GD.

  • Anti-TPO and TgAb: may also be elevated but are nonspecific.

Imaging

  • Radioactive iodine uptake (RAIU) and thyroid scan:

    • Diffuse uptake throughout the thyroid (distinguishes GD from thyroiditis or toxic nodules).

  • Ultrasound with Doppler:

    • Enlarged, hypervascular, hypoechoic thyroid (safe in pregnancy).

  • CT orbit: used in severe ophthalmopathy to assess orbital tissue enlargement.

Management

1. Symptomatic Treatment

  • Beta-blockers (e.g., propranolol, atenolol) for tachycardia, tremor, and anxiety.

    • Propranolol additionally reduces peripheral T4 → T3 conversion.

2. Antithyroid Drugs (ATDs)

  • Methimazole (MMI): first-line except in 1st trimester pregnancy.

  • Propylthiouracil (PTU): preferred in 1st trimester pregnancy or thyroid storm.

  • Side effects: agranulocytosis (rare but serious), hepatotoxicity, rash, arthralgia.

3. Definitive Therapy

  • Radioactive iodine ablation (RAIA):

    • Most common definitive treatment in adults.

    • Contraindicated in pregnancy and breastfeeding.

  • Surgery (thyroidectomy):

    • Indicated for very large goiters, suspicion of malignancy, intolerance to ATDs, or refusal of RAIA.

Special Situations

Graves Disease in Pregnancy

  • Differential diagnosis: must distinguish GD from hCG-mediated hyperthyroidism (e.g., hyperemesis gravidarum, trophoblastic disease).

  • Diagnostics: TRAb positive in GD, absent in hCG-mediated.

  • Treatment:

    • PTU in 1st trimester → switch to methimazole in 2nd–3rd trimester.

    • Surgery if uncontrolled on ATDs (safest in 2nd trimester).

    • RAIA is contraindicated.

  • Complications in pregnancy: intrauterine growth restriction (IUGR), prematurity, neonatal thyroid disease.

Neonatal Graves Disease

  • Cause: transplacental passage of maternal TRAbs.

  • Epidemiology: ∼5% of infants born to mothers with GD.

  • Clinical features:

    • Irritability, tachycardia, diaphoresis.

    • Hyperphagia but poor weight gain.

    • Goiter (can compress airway).

    • Possible craniosynostosis, microcephaly.

  • Treatment:

    • Usually self-limited (resolves within 1–3 months).

    • Symptomatic cases: methimazole + propranolol.

  • Complications if untreated: heart failure, developmental delay, intellectual disability.

Key Takeaways

  • Graves disease = autoimmune TSH receptor antibody–mediated hyperthyroidism.

  • Classic triad: diffuse goiter + ophthalmopathy + pretibial myxedema.

  • Diagnosis: suppressed TSH + ↑ T4/T3 + positive TRAb, confirmed with imaging if needed.

  • Treatment: symptom control + ATDs (methimazole/PTU) or definitive therapy (RAIA or surgery).

  • Special considerations: adjust therapy in pregnancy and monitor neonates of affected mothers.

 

Comments

Post a Comment