Abstract
That the anterior lobe of the hypophysis exerts a definite action on the thyroid gland seems well established. Although considerable work has been done (Loeb, 1 Riddle, 2 Schockaert, 3 Collip 4 ) it is yet a point of discussion as to which factor of the anterior lobe is responsible for this action. The preparation of a luteinizing and a follicular stimulating fraction in this laboratory (Fevold et al 5 ) has made it possible to test the thyroid stimulating ability of 2 extracts which differ widely in their physiological action on the ovaries. The gonadotropic ability of the extracts was determined before their thyreotropic action was tested. The follicular stimulating fractions used produced from 300 to 800% increase in weight of immature rat ovaries with production of little or no luteinization, while the luteinizing fraction even in comparatively large doses, had little or no effect.
A series of 9 young male and female guinea pigs from 3 to 12 weeks old were given subcutaneous injections of the luteinizing fraction (0.5 to 3 gm. equivalent pituitary powder) twice daily over a period of 5 days. The thyroid glands and ovaries were weighed and prepared for histological study 12 hours after the last injection. A similar group of 5 guinea pigs were injected with the follicular stimulating fraction (0.5 to 2 gm. equivalent). In each of these groups litter mate controls were kept and autopsied at the same time as the experimental animals.
The luteinizing fraction produced an increase in the weight of the thyroids of 50 to 145%, average 103%, over those of litter mate controls. At the time of autopsy these glands appeared swollen and highly vascular.
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