Page 556 - Concise Pathology for Exam Preparation ( PDFDrive )

20 Endocrinology 541

Q. Define and classify goitre. Describe the aetiopathogenesis, clinical
manifestations and morphology of the various types of goitre.
Ans. Goitre is defined as enlargement of thyroid gland.
Sequence of events in development of goitre (Flowchart 20.5):

Dietary iodine deficiency or intake of goitrogens

Decreased thyroid hormone synthesis

Compensatory increase in TSH

Hypertrophy and hyperplasia of thyroid follicular cells

Enlargement of thyroid (goitre)
Inadequate compensation
Diffuse nontoxic (simple) goitre Increased production of thyroid hormones
Multiple cycles of hyperplasia
and involution
Multinodular goitre Euthyroid state
FLOWCHART 20.5. Sequence of events in development of goitre.

1. Diffuse nontoxic (simple) goitre: Diffuse enlargement of the thyroid gland without
nodularity.
Types
(a) Endemic
(i) Common in Alps, Andes and Himalayas (labelled endemic when more than
10% of the population is affected)
(ii) Dietary supplements decrease incidence
(iii) Variation in prevalence of goitre in regions with similar levels of iodine
deficiency indicates the existence of other dietary influences, called
goitrogens, which may influence the prevalence rate.
(iv) Goitrogens, eg, vegetables of Brassicaceae and Cruciferae families (cab-
bage, cauliflower, Brussels sprouts, turnip and cassava) and excessive
calcium in the diet, interfere with thyroid hormone synthesis.
(b) Sporadic
(i) Less common than endemic goitre; females are affected more often than males.
(ii) Seen at the onset of pubertultsy or in young adults.
(iii) Associated with hereditary enzyme defects and ingestion of goitrogens; not
corrected by dietary supplements. There are four major types of enzyme defects:
- Iodide transport defect
- Organification defect (Pendred syndrome)
- Dehalogenase defect
- Iodotyrosine coupling defect
Morphology
Two morphological stages are identified, namely:
• Stage of hyperplasia
• Diffuse and symmetric enlargement of the thyroid
• Follicles are lined by crowded columnar cells with piling up of epithelium and formation
of pseudopapillary projections
• Variable colloid content in the follicles
• Stage of involution
• Starts if the dietary iodine increases or demand for thyroid hormones decreases
• Follicular epithelium involutes and becomes flattened

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