Table 6.8-2. Differential diagnosis of autoimmune and nonautoimmune hyperthyroidism

Criteria

Graves disease

Nonautoimmune hyperthyroidism (toxic MNG, solitary autonomously functioning nodule)

History

Recurrent hyperthyroidism; family history of autoimmune thyroid disease or other autoimmune diseases

Previous nontoxic MNG

Signs and symptoms of thyrotoxicosis

No differential features

Goitera

Features of vascular goiterb

MNG or solitary nodule

Ocular signs and symptoms

Features of orbitopathy (immunologic inflammation), overt orbitopathy in 20%-30% of patients, severe form of progressive ophthalmopathy with infiltrates and edema in 2%-3% of patients

Ocular signs and symptoms of sympathetic hyperactivity (lid lag and stare) do not preclude the diagnosis

Pretibial myxedema

1%-3% of patients

None

Laboratory thyroid function tests

↓ TSH and ↑ FT4 (less commonly ↑ FT3), no differential features

TRAb

95% of patients

Absent

↑ Anti-TPOc

70% of patients

15% of patients (elderly)

Thyroid Doppler ultrasonography (usually not necessary)

Diffuse vascularity of thyroid parenchymab

Nodules

Thyroid radionuclide scintigraphy

High uptake and homogeneous concentration of tracer

Autonomously functioning (hot) nodules and nonfunctioning (cold) areas

a Lack of goiter is not a differential feature.

b Nodules may be present in one-fourth of patients.

c Usually not indicated as not helpful in clarifying etiology (may also be present in healthy individuals and patients with nonautoimmune thyroid diseases).

↑, increased level; ↓, decreased level; anti-TPO, anti-thyroperoxidase; FT3, free triiodothyronine; FT4, free thyroxine; MNG, multinodular goiter; TRAb, thyroid-stimulating hormone receptor antibodies; TSH, thyroid-stimulating hormone.