THE SIMULTANEOUS DETECTION OF THYROID AND THYROTROPHIC HORMONES IN VERTEBRATE SERA

Abstract

The bioassay of thyroid-stimulating hormone (TSH) has been re-quantitated in the stasis (starved, nonmetamorphosing) tadpole with graded amts. (1.5-750 [mu]g.) of the International Gland Preparation of desiccated ox anterior pituitary. As little as 7.5 [mu]g. (0.0005 JS units) of the standard powder elevates mean thyroid cell height and increases hindlimb length (metamorphosis) in test animals. Thyroid activation and hindlimb extension parallel one another, with both responses a linear function of administered TSH. The stasis tadpole is also highly sensitive to thyroid principle. Several injns. of serum to which minute amts. of thyroxin are added (0.025 [mu]g-) re-initiate metamorphosis without causing significant change in the resting status of the thyroid. Bioassay "recovery" expts. with human sera, containing thyroxin and TSH in amts. previously assayed, demonstrate that the stasis animal can detect small amts. of these principles simultaneously in the same sample of serum without recourse to chemical or fractionation procedures. Phylogenetic studies, utilizing the technic, indicate that the thyroid-TSH balance in the circulating fluids of vertebrate may vary considerably. In rat serum, TSH concn. is high with little or no thyroid hormone detectable. Contrariwise, beef, human, lamb, horse, and guinea pig sera have appreciable thyroid but little or no TSH activity. The sera of lower vertebrates (frog, turtle) are ineffective, but pigeon serum has some TSH activity. The thyroid-TSH balance in blood can be altered experimentally; TSH, in rat serum, vanishes after hypophysectomy, and increases to a detectable level in the blood of goitrous guinea pigs.