Fig. 4
From: Relationship between caffeine intake and thyroid function: results from NHANES 2007–2012
Association between Serum TSH and Caffeine in Group 2 and Group 3. (A-B): Nonlinear Relationship Evaluation using the RCS Model. (C-D): Relationship between Serum TSH and Caffeine Intake using Multivariable Linear Regression in Group 2 and Group 3. Adjustments were made for race, age, BMI, drinking habits, cancer, comorbidities, urinary iodine, and intake of micronutrients (selenium, vitamin D, calcium, zinc, iron, magnesium) and macronutrients (protein, carbohydrate, and fat). Caffeine, TSH, urinary iodine, and micronutrient intake were log-transformed. A total of 12 subjects were excluded from regression in Group 2 due to missing data on urinary iodine, and 6 subjects were excluded from regression in Group 3 due to missing data in cancer (n = 1) and urinary iodine (n = 5)