The Inheritance of Thyroid Size and the Establishment of Thyroid Races in Ring Doves

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Abstract
Within a large colony of ring doves, mongrelized to a degree fairly comparable with that attained or attainable in mankind, physiological factors influencing thyroid weight have been controlled to an extent which has made possible a demonstration of genetic factors for thyroid size. Twenty-four strains or races have been studied, and at least 4 races with characteristically large thyroids and 4 races with characteristically small thyroids have been definitely established. This is the first demonstrated instance of the conscious establishment of a race on the basis of size or function of an endocrine gland. The surviving individuals of these races probably represent the nearest approach yet made to a biological standardization of an organism on the basis of thyroid size and function. This material is therefore specially suitable for the solution of a wide variety of biological problems. Ultimately it should particularly assist an interpretation of the relation of grades of thyroid function to certain physical traits in man. The attainment of this result was probably assisted by the choice of birds showing various types of reproductive disorder as the parents with which to initiate some of these races. A further selection for large or for small thyroid was practiced among progenies of the F1 and F2 generation. Crosses were made between races of all types[long dash]large, intermediate and small. Considering merely the average thyroid weight within each generation the results are as follows: Large thyroid Xlarge thyroid has given large thyroid in F1, F2 and F3. Small X small gives small thyroids in F1 F2 and (partly) F3. Intermediate Xintermediate tends (not always) to, give intermediate in F1, F2 and F3. Apparently large Xsmall yields thyroids of intermediate size in F1, F2 and F3. Questions of dominance, and of the number of genetic factors involved in thyroid size, must await the further accumulation of data from certain crosses. There is no suggestion of sex-limited inheritance of thyroid size in this material. The study is based on the thyroid weights of 1,931 healthy adult offspring of 50 parental ring doves whose thyroid size was also known.

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