THYROID FUNCTION IN THE FOETUS OF THE MACAQUE MONKEY (MACACA MULATTA)

Abstract

SUMMARY The foetal thyroid gland of the macaque monkey (Macaca mulatta) actively incorporates iodide and synthesizes thyroxine and its precursors monoiodotyrosine and diiodotyrosine. These iodinated components are retained in the foetal thyroid gland as they are synthesized, as has been shown by the uptake and distribution of 131I among the iodinated components and by the quantity of each component present in glands obtained from foetuses delivered by caesarean section 75, 90, 105, 120 and 150 days following conception. Butanol extractable iodine values of foetal serum, initially low, increase with foetal age and range from 1·2 to 4·5 μg./100 ml. serum at 75 and 150 days, respectively, while maternal values remain approx. 6 μg./100 ml. serum throughout pregnancy. Follicles of the foetal thyroid gland are present at 75 days following conception and progressively increase in number and size with increasing foetal age; colloid increases proportionately.