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Endemic goitre |
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Goitre may be endemic with more than 5 or 10 per cent of school children affected. This is normally associated with severe iodine deficiency. The goitre is due to thyroid cell replication induced by a concerted action of two physiological mechanisms: lack of iodine inhibition of the gland (iodine autoregulation) and stimulation of the gland by TSH (feed-back regulation induced by low thyroid hormone secretion due to lack of the substrate iodine).
A similar picture may be induced (or worsened) by goitrogens in food and water, certain drugs and smoking that inhibitits thyroidal utilization of iodine, primarily by interference with iodine uptake or organification in the follicular cells.
Congenital defects in one or more of the processes leading to thyroid hormone synthesis induce goitre, probably by similar mechanisms i.e. deficient iodine autoregulation (due to congenital defects in iodine utilization) and TSH stimulation. |
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