| Objective: Endemic goiter is one of the diseases that were found and diagnosed easiest of iodine deficiency disorders (IDD). But people pay more attention to the prevention and cure effects of iodine while neglect the effects of tyrosine, which is one of the essential materials to synthesis thyroid hormone. Consequently many experts are puzzled by some problems that not accord with the theory to prevent IDD only with iodine in some areas. This experiment was undertaken to clarify if tyrosine has effects on thyroid, and then to study the combined effects of iodine and tyrosine, and to provide evidence for the improvement of etiology and complete eradication of IDD.Methods: 96 healthy mice (weight 12~15g) were divided into 4 groups randomly according to 2×2 factorial experiment design, and every group has 12 male and 12 female mice: (1) Adequate iodine and adequate tyrosine (AIAT), (2) adequate iodine and low tyrosine (AILT), (3) low iodine and adequate tyrosine (LIAT) and (4) low iodine and low tyrosine (LILT). 120 days later, a blood sample was taken from medial canthus vein of each mouse, and the content of serum T3, T4, TSH was measured using radio-immunity method after the blood having been centrifuged. Then all animals were decapitated by breaking spinal cord at nuchae. Thyroids were weighted immediately and their relative weights were counted. The pathological changes of the tissue were observed with light microscope and electronic microscope. And the stereological indexes of thyroid such as S, V, Sf, G and NA were measured using correlated soft. All data was analyzed by SAS8.0.Results: 1. Compared with the AIAT group, in the LIAT group, the thyroid volume increased; the weight and the relative weight increased (P<0.01, P<0.01), and the value of the latter index was increased by 64.72%; the color of thyroid changed into ponceau from pink; light microscope: follicle and follicle cavity diminished. Follicle epithelial cells hyperplasied. Colloid reduced and distributed flocky. Blood capillary hyperplasied; electronic microscope: mitochondrion hyperplasied. Rough endoplasmic reticulum dilated. Some lysosomes emerged. The number of the microvilli increased and the colloid's electronic density lowered; the stereological indexes such as S, VA and Sf of the follicle and follicle cavity declined while G and NA went up; the content of serum T4 decreased while T3 and TSH ascended. The changes of the indexes above were significant (P<0.01). Compared with the AILT group, the thyroid of the LILT group enlarged markedly; the color changed into carmine from rosiness; the colloid quantity diminished evidently and there was no colloid in some follicle cavity when the specimen was observed with light microscope; some cilias appeared at the free side of the epithelial cell when with electronic microscope; the content of serum T3 changed with no significance (P>.05); other changes were id. 2. Compared with the AIAT group, thyroid of the AILT group enlarged appreciably; its weight and relative weight increased with no significance (P>0.05, P>0.05), and the value of the latter index was increased by 15.24%; the color changed into rosiness from pink; light microscope: epithelial cells expanded and arrayed multilayerly. Colloid reduced and distributed sieve-porely; electronic microscope: mitochondrion hyperplasied slightly and rough endoplasmic reticulum dilated ratherish; the stereological indexes such as S, VA and Sf of the follicle and follicle cavity declined while G and NA went up; the content of serum T4 reduced and T3, TSH increased. But the changes of the indexes above were not significant (P>0.05) except G (P<0.05). Compared with the LIAT group, thyroid of the LILT group enlarged continually and its weight and relative weight increased (P<0.01, P<0.01); color changed into carmine from ponceau; light microscope: follicle epithelial cells hyperplasied overly and the shape of the follicle was very irregular. Colloid disappeared. Blood capillary hyperplasied, dilated and was obviously hyperemic; electronic...
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