CORRELATION BETWEEN DAILY CAFFEINE INTAKE AND THYROID FUNCTION: A CROSS-SECTIONAL STUDY IN UNIVERSITY STUDENTS
Keywords:
Caffeine consumption, Thyroid-stimulating hormone (TSH), Thyroxine (FT4), University students, Endocrine health, HPT Axis, Dietary stimulants.Abstract
Background: Caffeine is the most widely consumed pharmacologically active compound among university students, used extensively to mitigate academic stress and sleep deprivation. However, its direct implications on the hypothalamic-pituitary-thyroid (HPT) axis and central endocrine pathways remain unclear.
Objective: To investigate the relationship between daily caffeine consumption and thyroid function parameters—specifically Serum Thyroid-Stimulating Hormone (TSH), Free Triiodothyronine (FT3), and Free Thyroxine (FT4) levels—in a university cohort.
Methods: A cross-sectional study was conducted with 40 healthy participants presenting an equal gender distribution (50% male, 50% female; mean age: 36.5 ±12.4 years). Habitual dietary caffeine intake was quantified using a validated Food Frequency Questionnaire (FFQ), stratifying subjects into Low (0–100 mg/day, n=13), Moderate (101–300 mg/day, n=14), and High (>300 mg/day, n=13) exposure tiers. Fasting morning venous blood samples were analyzed via Chemiluminescence Immunoassay (CLIA) techniques, and statistical analyses were performed using Pearson's correlation coefficient (r).
Results: The mean daily caffeine intake across the entire cohort was 214 ± 132 mg/day. A statistically significant, moderate-to-strong positive correlation was identified between daily caffeine consumption and serum TSH levels (r = +0.68, p < 0.05). Mean TSH advanced in a clear stepwise manner from 2.0 ± 0.2 mIU/L in the low group to 4.3 ± 0.2 mIU/L in the high group. Conversely, peripheral active thyroid fractions showed negligible, non-significant (NS) correlations with caffeine intake, with FT3 demonstrating a weak positive trend (r = +0.12, p > 0.05) and FT4 exhibiting a minor negative trend (r = -0.09, p > 0.05). Secondary gender stratification revealed higher mean TSH in males (3.4 mIU/L) than females (3.0 mIU/L), matching a higher baseline caffeine exposure among male participants (235 mg/day vs. 193 mg/day).
Conclusion: Daily caffeine consumption significantly correlates with elevated central pituitary TSH secretion in a dose-dependent framework. However, because peripheral hormones (FT3 and FT4) remain highly regulated within normal physiological bounds, this relationship represents a benign homeostatic adaptation rather than a clinical pathway toward thyroid disease.
