THE EFFECT OF GONADECTOMY ON THE THYROID GLAND IN THE GUINEA PIG1

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Abstract
Extirpation of the gonads in sexually mature young guniea pigs leads to an increase in the proliferative activity of the thyroid during the first week following the operation. There are in addition other changes indicating stimulation of the thyroid gland; of especial interest among the latter is an increase in the number of phagocytes which invade the colloid of acini, without undergoing early degeneration, and which may persist therefore for a longer period of time. In young immature guinea pigs these changes are less definite than in older ones. The stimulation of the thyroid accomplished by these means is on the whole very moderate and comparable to the effects obtained by administration of iodine preparations to guinea pigs rather than to the stimulation effected by optimal amounts of ant. pituitary extracts. Removal of the follicular hormone from a [female] guinea pig sets into motion not only a mechanism leading to an increase in the follicular growth and maturation-inducing hormone which represents a specific effect, but in addition it induces an increased production of the thyroid-stimulating hormone in the ant. pituitary, which must be considered as distinct from the hormone responsible for follicular growth and maturation; this second process represents, therefore, a nonspecific effect of gonadectomy on the ant. pituitary.