THE PITUITARY BODY 



activity is indicated morphologically by the atrophy of the 

 epithelium of the thyroid follicles and the distention of the 

 latter with dense, non-vacuolated colloid. Such changes were 

 again reported by Rowlands (1935), who hypophysectomized 

 fowls and mammals of several species (ferret, guinea pig, 

 and hedgehog). It is of interest that weight-atrophy does not 

 follow hypophysectomy in the guinea pig. The morphologi- 

 cal signs of inactivity of the thyroid could be observed in the 

 various animals 1-2 weeks after hypophysectomy." 



Other aspects of the biology of thyrotropic hormone. — The 

 most significant action of thyrotropic hormone is to facilitate 

 or promote the discharge of thyroid hormone from the thy- 

 roid gland. The colloid becomes vacuolated; the thyroid vesi- 

 cles diminish in size; the epithelial cells become hypertro- 

 phied. Its further effect is to promote hyperplasia of the 

 epithelium, so that doses much larger than those causing the 

 discharge of stored hormone may bring about marked hyper- 

 trophy of the thyroid. There still is disagreement as to the 

 unity or duality of the anterior pituitary hormone(s) causing 

 these two principal effects. 



Several new reports concerning the amount of hormone 

 in the pituitary body of various mammals have been pub- 

 lished. Miiller, Eitel, and Loeser (1935) declared that the 

 human gland contains 5-30 "guinea pig units." Undoubtedly 

 there was great variation in the degree of postmortem autoly- 

 sis in their material. The variations in potency were great 

 and appeared not be be related to age or sex; high values 

 were obtained if death was due to tuberculosis or other infec- 

 tions. According to Saxton and Uoeb (1937), the amount of 

 thyrotropic hormone in the human pars glandularis is quite 

 constant irrespective of age or other factors such as preg- 

 nancy and lactation. Rowlands (1936) used a reliable uni- 



' Reiss and Fischer-Popper (1936) injected 0.1-0.5 r"g- of thyroxine daily into 

 rats. They concluded that after hypophysectomy the sensitivity of such animals 

 was greatly increased (loss of body-weight, increased rate of urinary excretion of N, 

 increased basal metabolic rate), because compensating "antithyroid" effects of the 

 pituitary, mediated through the adrenal glands, were absent. 



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