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 TSH receptor antibodies: positive.
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.
INVESTIGATIONS
White blood cell count: elevated.
FNA biopsy: polymorphonuclear neutrophils. Gram stain shows organisms (bacteria, fungal hyphae).[30]
Toxic multinodular goitre
SIGNS / SYMPTOMS
Goitre generally is non-tender. Thyroid gland contains multiple nodules as seen by ultrasound.
INVESTIGATIONS
Serum TSH: 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.
Painful 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.[31]
INVESTIGATIONS
Radioactive iodine uptake: very low.
Serum antithyroid antibodies: positive.
FNA biopsy: lymphocytic infiltrate with varying degrees of fibrosis.
Thyroid cancer
SIGNS / SYMPTOMS
Anaplastic carcinoma may cause thyroid pain if rapidly growing. Thyroid texture may be firm to hard.
INVESTIGATIONS
Serum TFTs: normal.
Radioactive iodine uptake: normal.
Thyroid ultrasound: discrete thyroid nodule.
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.
Globus hystericus in the presence of goitre
SIGNS / SYMPTOMS
Thyroid is non-tender and soft.
INVESTIGATIONS
TFTs: normal.
Radioactive iodine uptake: normal.
Radioiodine thyroid scan: isotope distribution that is typical of a nodular goitre.
Exogenous thyroid hormone excess
SIGNS / SYMPTOMS
Either factitious or due to meat contamination by animal thyroid.[32]
INVESTIGATIONS
Radioactive iodine uptake: low or no uptake.
Thyroid ultrasound: normal.
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