Differentials
Graves' disease
SIGNS / SYMPTOMS
Thyroid is non-tender or minimally tender, compared with the extremely tender gland seen in subacute thyroiditis.
Graves’ disease may also have extrathyroidal manifestations, such as ophthalmopathy or pretibial myxoedema (thyroid dermopathy).
INVESTIGATIONS
Radioactive iodine uptake: high (>30%).
Radioiodine thyroid scan: diffuse uptake in an enlarged goitre.
ESR: normal.
Serum thyroid-stimulating hormone receptor antibodies and thyroid-stimulating immunoglobulins: positive.
Serum T3:T4 ratios >15:1 or >20:1.
Graves’ disease typically displays generalised increased vascular flow on power Doppler ultrasonography; normal or decreased vascular flow may be evident in patients with subacute thyroiditis.[45]
Infectious, suppurative, or acute thyroiditis
SIGNS / SYMPTOMS
Pharyngeal abscess is usually present, with dysphagia as a prominent symptom.
Unlike in subacute thyroiditis, there may be skin erythema over the painful thyroid.
Majority of cases may be due to bacterial infection.[30]
INVESTIGATIONS
White blood cell count: significantly elevated.
Ultrasound may be of benefit in early stages (prior to abscess formation); findings include perithyroidal hypoechoic space, hypoechoic area in the thyroid gland, and effacement of perithyroid tissue and thyroid gland.[30]
Fine needle aspiration biopsy: polymorphonuclear neutrophils. Gram stain shows organisms (bacteria, fungal hyphae).[46]
Toxic multinodular goitre
SIGNS / SYMPTOMS
Goitre generally is non-tender. Thyroid gland contains multiple nodules as seen by ultrasound.
INVESTIGATIONS
Serum thyroid-stimulating hormone: suppressed.
Serum T3 and T4 levels: mildly to moderately elevated.
ESR: normal.
Radioactive iodine uptake: mildly elevated.
Radioiodine thyroid scan: multiple areas of increased and decreased uptake in nodules within an enlarged thyroid.
Lymphocytic (silent) thyroiditis
SIGNS / SYMPTOMS
Absence of neck pain, symptoms of thyrotoxicosis, diffuse goitre.
INVESTIGATIONS
Radioactive iodine uptake may be variable: low, normal, or high.
ESR: normal.
Antithyroid antibodies: positive.
FNA biopsy (rarely required): lymphocytic infiltrate.
Hashimoto's (chronic lymphocytic) thyroiditis
SIGNS / SYMPTOMS
Symptoms of hypothyroidism may be present if the Hashimoto’s thyroiditis results in biochemical hypothyroidism.
A rare variant of Hashimoto’s thyroiditis may be associated with pain.[47]
INVESTIGATIONS
Serum antithyroid antibodies: positive.
FNA biopsy: lymphocytic infiltrate with varying degrees of fibrosis.
Thyroid cancer
SIGNS / SYMPTOMS
Anaplastic carcinoma may cause compressive symptoms to the anterior neck and thyroid pain if rapidly growing.
Thyroid texture may be firm to hard.
INVESTIGATIONS
Serum thyroid function tests: normal.
Radioactive iodine uptake: normal.
Thyroid ultrasound: discrete thyroid nodule(s).
Haemorrhage into a goitre or nodule
SIGNS / SYMPTOMS
Focal pain over the thyroid nodule. May be clinically indistinguishable from subacute thyroiditis.
INVESTIGATIONS
Radioactive iodine uptake: normal.
Radioiodine thyroid scan: area deficient in iodine uptake.
Thyroid ultrasound: discrete thyroid nodule with cystic degeneration.
Exogenous thyroid hormone excess (also known as thyrotoxicosis factitia)
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