Testing the short-and long-term effects of elevated prenatal exposure to different forms of thyroid hormones

Abstract

Maternal thyroid hormones (THs) are known to be crucial in embryonic development in humans, but their influence on other, especially wild, animals remains poorly understood. So far, the studies that experimentally investigated the consequences of maternal THs focused on short-term effects, while early organisational effects with long-term consequences, as shown for other prenatal hormones, could also be expected. In this study, we aimed at investigating both the short- and long-term effects of prenatal THs in a bird species, the Japanese quail Coturnix japonica. We experimentally elevated yolk TH content (the prohormone T4, and its active metabolite T3, as well as a combination of both hormones). We analysed hatching success, embryonic development, offspring growth and oxidative stress as well as their potential organisational effects on reproduction, moult and oxidative stress in adulthood. We found that eggs injected with T4 had a higher hatching success compared with control eggs, suggesting conversion of T4 into T3 by the embryo. We detected no evidence for other short-term or long-term effects of yolk THs. These results suggest that yolk THs are important in the embryonic stage of precocial birds, but other short- and long-term consequences remain unclear. Research on maternal THs will greatly benefit from studies investigating how embryos use and respond to this maternal signalling. Long-term studies on prenatal THs in other taxa in the wild are needed for a better understanding of this hormone-mediated maternal pathway.

Alternative Animal Models of Aging Research

“…Birds as oviparous vertebrates are widely used for the study of hormone functions on growth and development of the embryo (Groothuis and von Engelhardt, 2005), because the egg represents a closed system almost independent from maternal control once laid. The effects of the hormonal axes on growth, development, and aging can be tested by direct injection, e.g., of thyroid hormones into eggs (Sarraude et al, 2020). The latter increased telomere lengths in collared flycatchers and it was hypothesized that prenatal hormone exposure by this mechanism might set the aging clock in birds (Stier et al, 2020).…”

ASAS-NANP SYMPOSIUM: prospects for interactive and dynamic graphics in the era of data-rich animal science1

“…The experiment by Sarraude et al (2020) investigated the effects of prenatal thyroid hormones injections to quails on a number of traits (e.g., egg hatching success, embryonic development, and offspring growth). The eggs were injected with the prohormone ( ), its active metabolite ( ), a combination of both and ( ), or none (i.e., control eggs, CO).…”

“… Sarraude et al (2020) fitted a number of candidate models to the growth in body mass of quails using a nonlinear generalized additive mixed model. For illustration, we consider the model, henceforth referred to as the generalized additive model, that incorporated a temporal autocorrelation of the residuals using an autoregressive moving average ARMA(1, 1) model; a random intercept for the mother’s identity; treatment group, and sex as fixed effects; and thin plate regression spline for the age of the offspring varied by sex.…”

Is maternal thyroid hormone deposition subject to a trade-off between self and egg because of iodine? An experimental study in rock pigeon

“…Maternally transferred thyroid hormones play crucial roles in the development of the central nervous system (Darras, 2019) and several other tissues and organs (e.g., muscles, heart, eye, bones; McNabb and Darras, 2015). In addition, recent studies in birds have shown that physiological variation in prenatal THs can affect hatching success, growth and metabolism (Hsu et al, 2017;Hsu et al, 2019;Ruuskanen et al, 2016;Sarraude et al, 2020a).…”