Alterations of circadian rhythms of thyroid-stimulating hormone, thyroid, adrenal and insulin hormones, and blood glucose profiles following lithium treatment in alternate Light–Dark, constant Light and constant Dark regimens in rats

Lithium and endocrine disruption: A concern for human health?

Lithium is a key medication for the treatment of psychiatric disorders and is also used in various industrial applications (including battery production and recycling). Here, we review published data on the endocrine-disrupting potential of lithium, with a particular focus on the thyroid hormone system. To this end, we used PubMed and Scopus databases to search for, select and review primary research addressing human and animal health endpoints during or after lithium exposure at non-teratogenic doses. Given the key role of thyroid hormones in neurodevelopmental processes, we focused at studies of the neural effects of developmental exposure to lithium in humans and animals. Our results show that lithium meets the World Health Organization's definition of a thyroid hormone system disruptor - particularly when used at therapeutic doses. When combined with knowledge of adverse outcome pathways linking molecular initiating events targeting thyroid function and neurodevelopmental outcomes, the neurodevelopmental data reported in animal experiments prompt us to suggest that lithium influences neurodevelopment. However, we cannot rule out the involvement of additional modes of action (i.e. unrelated to the thyroid hormone system) in the described neural effects. Given the increasing use of lithium salts in new technologies, attention must be paid to this emerging pollutant - particularly with regard to its potential effects at environmental doses on the thyroid hormone system and potential consequences on the developing nervous system.

Constant light alters serum hormone levels related to thyroid function in male CD-1 mice

Disruptions to the circadian rhythm can lead to altered metabolism. Modification of thyroid function may be a reason why circadian misalignment may contribute to future metabolic disorders. We investigated whether circadian disruption through constant light (LL) can lead to variations in hormone levels associated with thyroid function. Mice were exposed to LL or a 12:12 Light:Dark (LD) cycle for 6 weeks; then glucose tolerance and thyroid hormone levels were measured at ZT 6 and ZT 18. There was day/night variation in glucose tolerance, but LL had no effect. LL reduced TSH, increased fT4, and abolished day/night variation in fT3 and leptin. These findings illustrate that LL alters thyroid-related hormones, providing evidence of a link between circadian disruption and thyroid function.