Differentials
Hashimoto's (chronic lymphocytic) thyroiditis
SIGNS / SYMPTOMS
Painless thyroiditis is considered by many to be a variant presentation of Hashimoto's thyroiditis. Patients with permanent hypothyroidism, early or after prolonged follow-up for painless thyroiditis, are indistinguishable from patients with Hashimoto's thyroiditis.
INVESTIGATIONS
No differentiating tests.
Graves' disease
SIGNS / SYMPTOMS
Orbitopathy, pretibial myxoedema, large goitre, a bruit over the thyroid, and more severe hyperthyroid symptoms.
Frequently indistinguishable based on symptoms and physical examination alone.[4]
INVESTIGATIONS
Positive for thyroid-stimulating hormone (TSH)-receptor antibodies (TRAb).
4-, 6-, or 24-hour radioiodine uptake elevated (or occasionally within the normal range), unless the patient has received a large amount of exogenous iodine (e.g., amiodarone).
Increased flow on colour-flow Doppler.
Toxic multinodular goitre
SIGNS / SYMPTOMS
Nodular goitre suggestive of diagnosis but does not exclude painless thyroiditis.
INVESTIGATIONS
4-, 6-, or 24-hour radioiodine uptake is normal or elevated, but it may be below normal if the patient has iodine-induced thyrotoxicosis (e.g., from radiocontrast). The pattern of uptake on radioiodine imaging (areas of increased and decreased uptake within the thyroid) is characteristic.
Should not be <1% unless the patient has received a large amount of exogenous iodine (e.g., amiodarone).
Factitious ingestion of thyroid hormone
SIGNS / SYMPTOMS
Rare presentation of thyrotoxicosis.
Goitre not usually present.
May not be distinguishable based on symptoms or examination alone, or even after extensive investigations.
INVESTIGATIONS
4-, 6-, or 24-hour radioiodine uptake and serum thyroglobulin low.[25]
Struma ovarii
SIGNS / SYMPTOMS
Very rare.
May present with pelvic discomfort but may not be distinguishable based on symptoms and physical examination alone.[26]
INVESTIGATIONS
4-, 6-, or 24-hour radioiodine uptake low over the thyroid gland, but measurable over the pelvis.
Subacute (granulomatous) thyroiditis
SIGNS / SYMPTOMS
Typically caused by viral infection.
Fever.
Hard and exquisitely tender thyroid gland.[27]
INVESTIGATIONS
Sedimentation rate (erythrocyte sedimentation rate) usually >100 mm/hour.
Suppurative (acute) thyroiditis
SIGNS / SYMPTOMS
Typically caused by bacterial infection.May present with anterior neck pain, swelling, tenderness, odynophagia, fever, chills, and local lymphadenopathy.[5]
INVESTIGATIONS
Thyroid function tests are typically normal with absent TPO antibodies. Blood cultures are positive for infecting pathogen.[5]
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