Recent advances in endocrinology / by A.T. Cameron.

  • Alexander Thomas Cameron
Date:
1947
Catalogue details

Licence: In copyright

Credit: Recent advances in endocrinology / by A.T. Cameron. Source: Wellcome Collection.

    19/466 page 7
    a small reserve of eolloid is always present. Subsequent to puberty the eolloid store inereases, and, as judged by the histolo¬ gical picture, activity slowly decreases (cf. Cooper), and this is in agreement with a slow decrease in basal heat production. Cooper has stressed the striking histological resemblance of the gland of the human adolescent and that considered characteristic of (untreated) Graves’ disease, and Abbott finds that this is true also for young domestic and wild animals ; the thyroids of older animals, as of man, store more colloid and present a histological picture suggesting lessening activity. Hoar has reported a some¬ what parallel picture in the thyroid of the Atlantic salmon. The interfollicular epithelial cells can produce new follicles whenever adequate stimuli activate the gland. This has been shown for rats by Baillif, using cold as stimulus. Seasonal changes in temperature are accompanied by histological changes in the thyroids of farm animals (cf. Kendall). Somewhat similar changes occur in the thyroids of women during the menstrual cycle. Pregnancy appears to produce a hyperplasia, probably accom¬ panied by an increase in function (Verdozzi; Abbott and Prender- gast). Different diets also produce some degree of change in the histological picture. Since under normal physiological conditions the histological picture of the thyroid can show such definite variations, it is evident that too great a differentiation of thyroid histology in pathological states may lead to error. The blood volume of normal man moves through his thyroid once an hour (Lerman). The blood supply of the thyroid is of importance in studying its pathological changes. Besides the four main arteries (paired superior and inferior thyroid arteries) and the occasional fifth (thyroidea ima) there are numerous unnamed irregular arteries, small in size under normal conditions, but capable of great enlargement in goitrous conditions ; they arise chiefly from the pharyngeal, oesophageal and tracheal arteries. Beneath the true capsule of the gland there is a rich arterial anastomosis. The veins commence as a perifollicular plexus and follow the small arteries to the periphery of the gland, there developing into a plexus covering the whole gland. The finer lymphatic radicles are present in intimate association with the follicular epithelium and a plexus exists around each follicle. By their union a coarser network is formed, with ultimately a close-meshed anastomosis enveloping the whole gland (cf. Joll). Control of Thyroid Secretion. It is frequently assumed that the
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