THE EFFECT OF THYROIDߚFEEDING ON THE WEIGHT OF THE SUPRARENALS AND ON THEIR ADRENALIN CONTENT

The administration of small quantities, 0·2 to 0·5 grm., of fresh ox thyroid daily to white rats increases the size and weight of the suprarenals both in young and adult animals. Reckoned in mg. per 100 grm. body-weight, the extent of the increase in the eighteen male animals examined averages a figure which is equivalent to a rise in weight of from 76 to 78 per cent. above the normal. This is the result of feeding the animals with the above-mentioned doses of thyroid for a period of from three to four weeks. Both cortex and medulla participate in the enlargement, but the hyprotrophy of the cortex is somewhat greater than that of the medulla. There is reason to believe that where accessory suprarenals are present they too undergo enlargement. The adrenalin content of the suprarenals of the white rat increases as a general rule with increase in weight of the animal. The amount of adrenalin normally present is about 0·034 mgr. per 100 grm. body-weight. Feeding with thyroid increases the adrenalin content of the suprarenals. The average amount in the eighteen animals examined averages from 0·049 to 0·052 mg., which is equivalent to a rise in weight of about 50 per cent. Owing to the relatively greater increase in weight of the suprarenals, resulting from thyroid-feeding, the percentage amount of adrenalin in them is decreased, though only to a small extent. It is probable that the adrenalin in the accessory suprarenals, when these are present, is also increased. Rats fed with small doses of thyroid not infrequently die suddenly when apparently thriving. In the animals examined which have thus died there is great increase in the weight of the suprarenals and in the adrenalin content. The heart is greatly hypertrophied in addition. There is evidence that thyroid-feeding results in rapid cardiac hypertrophy in white rats. The condition is being further investigated. The author has to thank Mr Niven of Strathkinness for his kindness in ensuring a regular supply of fresh ox thyroids. The expenses of the research have been met by a grant from the Carnegie Fund.