The hypothalamus-pituitary-thyroid-axis (HPT) is one of the main neuroendocrine axes that control energy expenditure. The activity of hypophysiotropic thyrotropin releasing hormone (TRH) neurons is modulated by nutritional status, energy demands and stress, all of which are sex dependent. Sex dimorphism has been associated with sex steroids whose concentration vary along the life-span, but also to sex chromosomes that define not only sexual characteristics but the expression of relevant genes. In this review we describe sex differences in basal HPT axis activity and in its response to stress and to metabolic challenges in experimental animals at different stages of development, as well as some of the limited information available on humans. Literature review was accomplished by searching in Pubmed under the following words: “sex dimorphic” or “sex differences” or “female” or “women” and “thyrotropin” or “thyroid hormones” or “deiodinases” and “energy homeostasis” or “stress”. The most representative articles were discussed, and to reduce the number of references, selected reviews were cited.
Exposure to chronic stress during adolescence causes long-term effects on the response of Hypothalamus-Pituitary-Adrenal (HPA) axis, affecting behavior and energy homeostasis. Voluntary exercise activates the HP-Thyroid (HPT) axis allowing efficient fluxes of substrates to active target organs. Chronic stress in adult rats blunts HPT axis response to voluntary exercise in a sex-dependent manner (Front Endocrinol 10(418):1-13, 2019). As adolescents show sex-dependent responses to stress, we sought to evaluate the effect of chronic stress at this period in the response of HPT axis to voluntary exercise in adulthood. Wistar male and female rats were divided in an undisturbed group (Control, C) and one group exposed to chronic variable stress (CVS) where the rats were daily subjected to different stressors during postnatal day (PND) 30 to 60 for females and PND 30 to 70 for males. At adulthood (PND 74 for females and PND 84 for males) rats were exposed to running wheel following published protocol (Endocrinology 155:2020-2030, 2014). As females are more susceptible to stress during adolescence than males, additional independent experiments were performed with female rats kept in group or individual housing, since PND 30 (2 per cage or isolated (Iso)). At PND 64, Iso rats were housed in pairs and exposed to CVS every 3 days until PND 80; later, rats were exercised 26 days. Hormones were quantified by ELISA or RIA; mRNA expression was determined by RT-PCR. Voluntary exercise reduced fat mass in C groups, dependent on the amount of exercise performed; stressed rats exercised did not lose fat, indicating that adolescent stress avoids an appropriate energy distribution during exercise. The expression of Crh and Avp in hypothalamic paraventricular nucleus (PVN) decreased in stressed groups mainly in females, as reported. Exercise decreased corticosterone levels only in C rats, suggesting that CVS during adolescence modifies the HPA axis response to exercise. CVS inhibited Pomc expression induced by exercise and increased Npy expression in arcuate nucleus, decreased Trh expression in PVN for both sexes and in dorsomedial hypothalamus in males. Thyroid hormones were not altered in CVS males and Iso females; however, T3 and T4 levels were high in CVS females, so different stress exposures may modify the HPT axis state in females. The response to exercise of the target organs of thyroid hormones reveals with more accuracy the activity of HPT axis, exercise stimulated the expression of Adrb3 and Dio2 in brown adipose tissue of C females, and the expression of Dio2 and Pgc1a in skeletal muscle (gastrocnemius) of both sexes, changes attenuated by CVS. These results indicate that chronic stress during adolescence blunts the response of HPT axis to voluntary exercise, strongly in females than males.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.