34 The Endocrine Organs 



tendency for colloid to accumulate. This ultimately causes enormous dis- 

 tension of the vesicles and flattening of their epithelium (fig. 23), which 

 may eventually undergo almost complete degeneration. A characteristic 

 degeneration of the arteries of the gland has also been described. 



Whilst the above are the usual changes found in endemic goitre, many 

 exceptions are met with. One would expect the enlarged gland to yield 

 an excessive amount of secretion to the blood, but this appears not to be the 

 case, although endemic goitre is occasionally characterised in its early stages 

 by symptoms suggestive of hypersecretion and resembling some of those 

 seen in incipient exophthalmic goitre (p. 37). More often these symptoms 

 of hyperthyroidism are absent : generally from the first and always 

 eventually, the appearances which show themselves are unquestionably 

 symptomatic of hypothyroidism. This must mean that even if the 

 secretion is being produced in abundance it is not of a normal character, 

 the normal autacoid being either absent or deficient in quality. Perhaps 

 the enlargement of the gland represents an attempt by nature to compensate 

 for such deficiency. 



