Struma
Goiter (rarely thyromegaly) refers to enlargement of the thyroid gland. It can occur from multiple conditions. Clearly the absence of thyroid enlargement does not preclude significant thyroid pathology.
The definition of a goiter depends on age and sex; below are the upper limits of normal for thyroid gland volume :
- adult males: 25 mL
- adult females: 18 mL
- 13-14 years: 8-10 mL
- 3-4 years: 3 mL
- neonate: 0.8-1.5 mL
Epidemiology
The prevalence of goiter varies widely depending on the level of iodine deficiency. In severely iodine-deficient areas the prevalence may be as a high as 80%. Goiter is more common in women (M:F = 1:4) and incidence declines with age .
Pathology
The thyroid gland may become so enlarged that it becomes a substernal (retrosternal) goiter.
Etiology
The causes of goiter are diverse :
- non-toxic simple goiter (e.g. from iodine deficiency)
- Graves disease
- multinodular goiter
- Hashimoto thyroiditis
- thyroid cancer
- goitrogens
- drugs: lithium, amiodarone, etc.
- diet: cabbage, sprouts, etc.
- depositional disease, e.g. amyloidosis
- miscellaneous, e.g. Plummer-Vinson syndrome
Radiographic features
Ultrasound/CT
- each lobe normally measures :
- length: 4-7 cm
- depth: <2 cm
- isthmus ≤0.5 cm deep
Thyroid volume can be estimated by measuring each lobe and applying the following correction factor for an ellipsoid formula :
- height (cm) x width (cm) x depth (cm) x 0.529*
* various correction factors between 0.494-0.554 have also been proposed
- volume (excluding isthmus, unless its thickness is >3 mm)
- 10-15 mL for females
- 12-18 mL for males
History and etymology
Goiter derives from the old French "goitron" meaning gullet. Goitron comes from the Latin "guttur" meaning throat.
Differential diagnosis
See main article: midline neck mass
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