[Effect of theophylline on the thyroid function in healthy subjects: comparison between the short- and long-term medication].

Effect of theophylline on the thyroid function was studied in 9 healthy subjects. Theophylline (200mg) was taken two times (AM8:00, PM10:00) and blood was collected two times (AM9:00, PM4:00) a day for five days. Five of these 9 subjects took same dose two times (AM8:00, PM10:00) a day and blood was collected once (AM9:00) a week for four weeks. In short-term medication, serum free thyroxine (FT4) increased significantly (1.19 +/- 0.19 ng/dl, before medication) in 4th day AM (1.29 +/- 0.14 ng/dl, p < 0.05), in 4th day PM (1.30 +/- 0.12 ng/dl, p < 0.05) and in 5th day AM (1.30 +/- 0.16 ng/dl, p < 0.05). Serum free triiodothyronine (FT3) increased significantly (3.9 +/- 0.36 pg/ml, before medication) in 4th day AM (4.3 +/- 0.66 pg/ml, p < 0.05) and in 5th day AM (4.3 +/- 0.61 pg/ml, p < 0.05). Serum thyroid stimulating activity (TSA), which was measured as an increase in cAMP in FRTL-5 cells, increased significantly (116.5 +/- 49.5%, before medication) in 1st day PM (152.3 +/- 60.0%, p < 0.05), in 2nd day PM (192.6 +/- 86.7%, p < 0.05), in 3rd day PM (208.5 +/- 94.1%, p < 0.05) and in 4th day AM (183.5 +/- 80.1%, p < 0.05). In contrast, serum FT4, FT3, TSH, and TSA did not increase significantly in long-term medication.(ABSTRACT TRUNCATED AT 250 WORDS)