A preliminary study of thyroid hormones and thyroid ultrasonographic images in normal Chinese rhesus monkeys (Macaca mulatta)

Abstract

Objective: Our study aims to explore the relations among thyroid morphology and hormones and sex, age in rhesus monkeys, so to establish a range of reference values for serological testing of thyroid hormones and thyroid ultrasonography in Chinese rhesus monkeys. Furthermore, we analyze the common diseases and incidences of abnormal thyroid morphology in these monkeys. Methods: 1027 rhesus healthy monkeys were divided into infant, juvenile, adolescent, adult, middle-aged, and elderly groups based on their age. The thyroid hormones (TT3, TT4, FT3, FT4, TSH, A-TG, ATPO, TG) levels of each rhesus monkey were measured. Thyroid ultrasonography was performed and thyroid size, morphology, internal echogenicity, borders, presence of nodules were measured. Comparisons between groups were made by ANOVA, and comparisons within groups were made by T-test; Pearson's analysis was used to test the correlation between the two variables. We considered that α=0.05, and P<0.05 was statistically significant. Results: The thyroid hormones tests found that there are differences in TT4, FT4, FT3, A-TG, A-TPO, and TG in different age groups (p<0.05). The differences in their FT4, FT3, A-TG, and TG were statistically significant in different genders (p<0.05), too. Thyroid ultrasound measurement of thyroid size revealed statistically significant (p<0.05) differences in their weight and thyroid LAPD, LLD, RAPD, RTD, RLD by age. There are also statistically significant (p<0.05) differences in their weight and thyroid LAPD, LLD, RLD by gender. In thyroid ultrasonography, about 14.12% of monkeys were found to have abnormal thyroid echoes, of which 71.72% were described as uneven echoes, 16.55% as grid-like changes in thyroid echoes, and 11.72% as thyroid nodules. Normal thyroid echogenicity was associated with age, body weight, TT4, TT3, FT4, FT3, and statistically significant difference (p<0.05); the rest of the group comparisons were not statistically significant (p>0.05).TT4 vs. FT4, TT3 vs. FT3, ATG vs. ATPO, body weight vs. LLD, body weight vs. RLD, LLD vs. RLD, LAPD and RAPD, and RAPD and RLD were positively correlated (p<0.05). Conclusion: Our study provided a reference basis for quantitative analysis of thyroid hormones and morphology in monkeys through serological testing of thyroid hormones and thyroid ultrasonography. In this way, we initially established reference intervals for various hormonal indicators of thyroid hormones in Chinese rhesus monkeys of different ages and sexes, as well as reference intervals for the size of thyroid morphology by diameter under ultrasonography for different ages and sexes. We explored the types of abnormalities and prevalence of abnormalities of thyroid morphology in Chinese rhesus monkeys. The results provide basic information for scientific experimental studies on the thyroid gland of Chinese rhesus monkeys.