Relationships of Adrenals, Gonads, and Thyroid to Thymus and Lymph Nodes, and to Blood and Thoracic Duct Leukocytes

The effects of gonadectomy, adrenalectomy, and thyroidectomy, and of thyroxine administration on the weight of lymphatic tissues and on the numbers of blood and thoracic duct leukocytes have been studied over a 40 day period in young male rats. The results of the present experiment are interpreted to indicate that:

1. Removal of the gonads caused a marked increase in the weight of the thymus, whereas but slight effect was noted on the weights of the lymph nodes. Removal of the adrenal glands, however, resulted in a marked increase in the weight of all lymphatic tissues.

2. Thyroxine administration was demonstrated to exert a hyperplastic effect on the lymph nodes, an effect which was accentuated by the removal of the adrenals and gonads. The lymph nodes were more sensitive than the thymus to the stimulating influence of thyroxine administration in the intact animal.

3. A comparison of the weights of the thymus and lymph nodes to control values was more indicative of the hypoactivity or hyperactivity of the thyroid, adrenals and gonads, than were the weights of the thymus or lymph nodes considered separately.

4. The increase in the level of blood lymphocytes following removal of the adrenals appeared to result from a failure of normal removal of the lymphocytes from the bloodstream, rather than from an increased delivery of the lymphocytes to the bloodstream via the thoracic duct. Administration of thyroxine to normal animals did not produce a blood lymphocytosis, lending further weight to the suggestion of Marine and others that the blood changes seen its toxic hyperthyroidism are the result of adrenocortical insufficiency.

5. Changes in the weight of the lymphatic tissues were not necessarily reflected by a proportional change in the number of thoracic duct lymphocytes, nor did the number of blood lymphocytes necessarily reflect the number of lymphocytes delivered to the bloodstream via the thoracic duct lymph.

6. The marked increase in the volume and cell content of thoracic duct lymph noted its thyroxine treated adrenalectomized-gonadectomized animals appears to be directly related to an increased sensitivity to the effects of thyroxine administration in the absence of these glands.

7. Removal of the thyroid gland vitiated the increases in weight of thymus and lymph nodes produced after castration and/or adrenalectomy.

8. The eosinophilic leukocytosis consequent on adrenalectomy was markedly augmented by removal of the thyroid and gonads.