Timing of seasonal breeding in birds and mammals is regulated by changing the day length and is dependent on the presence of thyroid hormones. A mechanism for thyroid-dependent control of seasonality has been proposed, in which exposure to long day lengths induces rapid local conversion of T4 to its bioactive form, T3, via the up-regulation of the enzyme type 2 iodothyronine deiodinase (Dio2) in the brain, and the down-regulation of Dio3 (which inactivates T3). Such changes were correlated with gonadotropin release and gonadal growth in quail. This mechanism was elucidated in a domesticated species (quail) exposed to unnatural acute changes in day length. Here we investigated the Dio2/Dio3 mechanism in a wild species, the European starling, under naturally changing day length. Although Dio2 expression varied seasonally, Dio3 did not. We found no correlation of Dio2 with photoperiod, seasonal regulation of GnRH, or testicular volume. The observed differences in data from starlings and quail could be a result of phylogeny, genetic drift from founder populations, or differences in reproductive seasonality in addition to or instead of arising from domestication or use of artificially changing photoperiods. Overall, the data indicate that in a wild species exposed to natural changes in day length, the current proposed mechanism for photoperiodic timing is less straightforward than is generally accepted and might not be as universally applicable as previously thought.
Purpose of Review While obesity-related comorbidities are frequently addressed and treated in primary care (PC), obesity itself is undertreated. We review the current treatments for obesity and provide potential provider and system-level strategies for integrating weight management and improving longer term obesity care within PC settings. Recent Findings We now understand that the body develops multiple mechanisms to resist weight loss and promote weight regain, making both weight loss and weight loss maintenance challenging. Therefore, weight management often requires medically supervised interventions and should be treated on a long-term basis. However, there are multiple barriers to improving obesity care within PC settings. Summary Clinically, utilizing strategies such as a shared decision-making approach and the 5As to discuss treatment options can facilitate formulating an obesity treatment plan. Utilizing telehealth, a team-based approach, and community partnering can increase patient access to intensive behavioral interventions. Future studies should evaluate other cost-effective methods to implement obesity care into the PC setting.
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