Jolly(l), Halpenny and Thompson(2) supported this view, but. during secretory activity and can be traced to the tubes of the parathyroid.

Transcription

1 EFFECT OF PARATHYROID FEEDING ON THE THYROID. BY DOROTHY WOODMAN. (From the Department of Physiology, London (R.F.H.) School of Medicine for Women.) Two hypotheses have been put forward to explain the relationship of the thyroid and parathyroid. The first one suggests that the two glands are' so related in function that a deficiency of the one is compensated for by hypertrophy of the other. The older experiments of Vincent and Jolly(l), Halpenny and Thompson(2) supported this view, but Vincent and Arnason(3) were unable to confirm their results. Scott Williamson (4) believes the thyroids and parathyroids are related anatomically, physiologically and pathologically. He suggests that a fluid matter (not colloid) is found in the sinusoids of the thyroid during secretory activity and can be traced to the tubes of the parathyroid. The second hypothesis suggests that though the two glands are related anatomically they are antagonistic in their physiological function. This is well supported by a comparison of their effects on calcium metabolism. The chief differences between the two glands have been summarised by Cowdrey(5) by a comparison of the effects produced by atrophy, removal or administration of extracts of the two glands. The following experiments were carried out to show the effect of parathyroid feeding on the structure of the thyroid, and hence obtain information with regard to the functional relationship of the two glands. Very few experiments correlating the respective functions and structure of the thyroid and parathyroid havebeen carried out. K oj im a (6) fed rats with parathyroid but his results are not satisfactory as the rats had previously been fed with thyroid. Halpenny and Thompson(2) give diagrams which indicate that after parathyroidectomy the vesicles of the thyroid are larger, more irregular, and appear more active. Methods. Adult and young rats ments. of both sexes were used for these experi-

2 558 D. WOODMAN. Feeding. The actual method of feeding and the diet given is reported by Woodman(7). Doses of 002 grm. desiccated parathyroid were given daily for periods varying with the different series from 2-5 weeks. The rats were weighed twice a week. Histology. The rats were killed by chloroform and a small portion of the trachea, to which the thyroid and parathyroids were attached, removed, fixed in formal-acetic-muller and prepared for embedding in the usual way. The appearance, especially the colour, of the thyroid was noticed on removal. The slides were examined to determine the degree of activity of the thyroid at death, the degree of activity being judged by the following points: (a) The amount of colloid-and its appearance, i.e. degree of staining, and presence or absence of vacuoles. (b) Character of vesicular epithelium-whether flattened, cubical, or columnar. (c) Size, number and irregularity in shape of vesicles. Points (a) and (b) were specially observed, since several observers have put forward the view that the amount of stored colloid (and therefore the type of vesicular epithelium) varies inversely with the degree of activity of the gland (Courrier(s), Scott Williamson(4)). Parathyroid. The parathyroid was examined to determine if any structural change had occurred, special attention being paid to the fact that wide variations in types of cells and amounts of fibrous tissue are normally found. Results. The effects of the parathyroid feeding on the structure of the thyroid were so consistent that only a summary is given. These results were obtained from (a) six litters of young rats including 48 rats of both sexes; (b) 29 adult rats of both sexes. Control. Thyroid. Typical appearance. Fair amount of colloid present, vacuolated in many cases. Epithelium cubical or columnar. Gland appeared resting or active and in most cases very vascular (see Fig. 1). Parathyroid. Vascular in many cases. Variation in amounts of fibrous tissue present was founid. Parathyroid-fed rats. Thyroid. Appeared inactive in every case. Inactivity most marked in rats fed with parathyroid for longer period. Vesicles distended with colloid and in some cases so distended as to give an appearance similar to "colloid goitre" (see Fig. 2).

3 PARATHYROID AND THYROID. 559 Fig. 1. Thyroid (control). Note small vesicles. Columnar epithelium. Vacuolated colloid. Fig. 2. Thyroid (parathyroid-fed animal). Note larger vesioles distended with colloid. Epithelium flattened.

4 560 D. WOODMAN. Parathyroid. Adult rats showed more fibrous tissue than young rats, but on the whole the amount of fibrous tissue present lay within the limits of the normal variations. Discussion of Results. Parathyroids. The parathyroids of controls are generally formed of masses of cells, and only traces of fibrous tissue are found. On the other hand, the parathyroids of experimental rats appeared in most cases to consist of cells more loosely arranged and separated by islands or strands of fibrous tissue. Hoskins(9) and McCarrison(lo) have both pointed out that the parathyroid may either consist of compact masses of cells and no strands of fibrous tissue, or the cells may be more loosely packed and separated by well-marked reticular tissue. McCarrison states that both types may even be seen in the same glandule. Since these variations in structure may be found in the normal gland, the apparent increase of fibrous tissue in several of the parathyroid-fed rats cannot be ascribed to a specific effect of the parathyroid feeding. Thyroid. Macroscopically, the thyroids of rats which had received parathyroid were a pale pink in colour as compared with the healthy red colour of controls. This change in colour of the thyroid was also found by Cameron and Carmichael(ni) after thyroid feeding, which, as is discussed below, produced the same histological effect as reported here after parathyroid feeding. Histologically, the appearance of the thyroid in the rats which had received parathyroid was quite different from that in the controls. The vesicles were large, distended with colloid, and vesicular epithelium was flattened. The effect was more marked where animals received parathyroid for a longer time. The assumption is, that parathyroid feeding, since it produces an accumulation of colloid in the gland, has inhibited the activity of the thyroid. These results might be interpreted in two ways, either in support of the suggestion that the thyroid and parathyroid are compensatory to a certain extent, or that they are antagonistic in function. Cameron and Carmichael(iu) and Kojima(6) reported that thyroid feeding produced an inactive appearance of the thyroid. The results of parathyroid feeding appear to produce an identical change in the thyroid and therefore suggest, at first sight, that the two glands have a similar function and are able to compensate for each other. But, if the effect of parathyroid feeding is to replace the function of the thyroid in the body thereby causing a storage of its colloid, then one would expect similar changes in body weight and growth to those produced by

5 PARATHYROID AND THYROID. thyroid feeding. It has already been reported by Woodman(7), that no marked effect on growth was found after parathyroid feeding, and certainly not the decrease in weight which is found with thyroid feeding. Thus it is questionable whether the inhibition of the thyroid is due to a replacement of its function by the parathyroid. On the other hand, the influence of the thyroid and parathyroid on both calcium and carbohydrate metabolism has suggested that they are antagonistic. Koj ima(6) found a storage of colloid in the thyroid after parathyroid feeding but did not continue to investigate whether the effect was due to the parathyroid or to previous thyroid feeding. The results of the experiments reported here suggest that his results were due to the parathyroid feeding. Critchley(12) reported that 11 cases of Graves' disease were treated with parathyroid, and in every case nervousness and tachycardia were diminished, and in five cases the goitre was reduced. The results of the experiments reported here taken in conjunction with the above report of Critchley and the results of Halpenny and Thompson(2) suggest that the parathyroid normally inhibits the thyroid. SUMMARY AND CONCLUSIONS. (1) Administration of parathyroid produces no marked structural change in the parathyroid. (2) The thyroid of rats fed on parathyroid presents an inactive appearance as shown by the increased amount of colloid presont and the distension of the vesicles. (3) It is suggested that the effect of parathyroid feeding on the thyroid is due to the antagonism of the two glands rather than to a replacement of the thyroid function by the administered parathyroid. In conclusion I wish to thank Prof. Cullis for her help and criticism throughout this work, and also the Royal Society for a grant allotted towards the expenses incurred. REFERENCES. 1. Vincent and Jolly. This Journ. 32. p Halpenny and Thompson. Anat. Anzeig. 34. p Vincent and Arnason. Endoc. 4. p Scott Williamson. Lancet, ii. p Cowdrey. Endoc. and Metab. 1. p Kojima. Quart. Journ. Exp. Phys. 11. p Woodman. Biochem. Journ. 19. No. 4. p Courrier. Compt. Rend. Soc. Biol. 86. p Hoskins. Endoc. 8. p McCarrison. The Thyroid Gland. p. 11. (Bailliere Tindall & Cox.) 11. Cameron and Carmichael. Journ. Biol. Chem. 45. p Critchley. The Practitioner, 113. No. 1. p PH. LXI