THE CONTEXT
Simple goitre can develop through thyroid stimulation by TSH and other growth factors. Iodine deficiency and defective hormone synthesis contribute to different patterns of disease.
TSH-mediated thyroid stimulation
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TSH can stimulate thyroid enlargement in response to chronically low circulating thyroid hormone levels.
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Rarely, inappropriate TSH secretion from an anterior pituitary microadenoma causes this stimulation.
Endemic and sporadic goitre
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Dietary iodine deficiency is the most important factor in endemic goitre.
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Defective hormone synthesis probably accounts for many sporadic goitres.
Other growth stimuli and nodularity
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Thyroid follicular cell proliferation is influenced by growth factors other than TSH, including immunoglobulins.
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The heterogeneous structural and functional response producing characteristic nodularity may reflect cell clones that are particularly sensitive to growth stimulation.