Intermittent Fasting and Thyroid Hormone Regulation: Impacts on Metabolic and Endocrine Health During Ramadan

Intermittent fasting, especially during Ramadan, has gained increasing attention for its effects on metabolic and endocrine health, notably through thyroid hormone regulation. This review synthesizes current literature on the impact of fasting patterns on thyroid hormones such as TSH, T3, and T4, highlighting variations influenced by fasting duration, sex, age, exercise, and medication. The metabolic outcomes, including alterations in glucose homeostasis, insulin sensitivity, lipid profiles, and body composition, are evaluated alongside endocrine markers beyond thyroid hormones, such as sex steroids and cortisol. Mechanistic insights explore modulation of the hypothalamic-pituitary-thyroid axis, molecular pathways involving deiodinases and transport proteins, circadian rhythm interplay, and hormonal crosstalk with leptin, ghrelin, and glucocorticoids. Special focus is given to vulnerable populations like women and diabetic patients. The review identifies significant inter-individual variability and underscores the importance of personalized approaches, diet composition, and nutritional status. Gaps remain concerning the long-term effects of Ramadan fasting on thyroid function and the development of molecular biomarkers for monitoring. These findings highlight the necessity for further research to optimize health outcomes and provide ethical guidance for practicing Ramadan fasting in diverse populations.