Thyroid Health and Low-Carb Diets: What Lower T3 Really Means

This week in The Metabolic Classroom, Ben explores the effects of a ketogenic diet on thyroid function, addressing concerns that lower thyroid hormone levels observed during the diet may indicate dysfunction. Dr. Bikman begins by explaining the hypothalamic-pituitary-thyroid (HPT) axis, a regulatory system that controls thyroid hormone production. The thyroid gland produces two primary hormones, T3 (triiodothyronine) and T4 (thyroxine), with T3 being the active form that influences metabolic processes. He emphasizes the concept of negative feedback within the HPT axis, explaining that normal TSH levels generally indicate a well-functioning thyroid, even if T3 levels are lower. Ben also reviews a commonly cited study that observed decreased T3 levels in individuals following a ketogenic diet. Despite the drop in T3, TSH levels remained normal, suggesting that the thyroid gland was not damaged but rather adapting to reduced metabolic demand. He introduces two key explanations: improved thyroid hormone sensitivity and reduced glucose metabolism. Improved sensitivity means that lower levels of T3 are sufficient to maintain metabolic functions, while reduced glucose consumption on a ketogenic diet lessens the body’s need for thyroid hormone to regulate glucose uptake. The classroom lecture then delves into the concept of thyroid hormone resistance, a condition linked to metabolic disorders like obesity and type 2 diabetes. Dr. Bikman references studies showing that thyroid resistance is real and measurable, often associated with elevated TSH and thyroid hormones in individuals with metabolic syndrome. He speculates that a ketogenic diet may enhance thyroid sensitivity in these individuals, reducing the need for higher T3 levels. In conclusion, Dr. Bikman reassures those on a ketogenic diet that lower T3 levels do not necessarily indicate harm. If TSH levels are normal and no symptoms of hypothyroidism are present, the changes may reflect a healthy adaptation to the metabolic state induced by the diet. Show Notes/References: For complete show notes and references referred to in this episode, we invite you to become a Ben Bikman “Insider” subscriber. As a subscriber, you’ll enjoy real-time, livestream Metabolic Classroom access which includes live Q&A with Ben, ad-free Metabolic Classroom Podcast episodes, show notes and references, Ben’s Research Reviews Podcast sent to your inbox weekly, and a searchable archive that includes all Metabolic Classroom episodes and Research Reviews. You can learn more about becoming an Insider on our website: https://www.benbikman.com Ben’s favorite yerba maté and fiber supplement: https://ufeelgreat.com/usa/en/c/InsulinIQ Ben’s favorite meal-replacement shake: https://gethlth.com (discount: BEN10) Ben’s favorite electrolytes (and more): https://redmond.life (discount: BEN15) Ben’s favorite allulose source: https://rxsugar.com (discount: BEN20) Ben’s favorite health check-up for women: https://choosejoi.co/drben15 (discount: DRBEN15) Ben’s favorite exogenous ketone: https://www.americanketone.com (discount: Ben10) Hosted on Acast. See acast.com/privacy for more information.