title: Modulation of thyroidal radioiodine uptake by theophylline.
abstract: Diagnostic and therapeutic use of radioiodine in the management of thyroid disorders depends on the ability of thyroid cells to concentrate radioiodine, a process regulated by thyrotropin and dependent on the intracellular increase in cAMP. We tested the ability of theophylline, a drug known to increase intracellular cAMP via inhibition of phosphodiesterase, to modulate the thyroidal radioiodine uptake in FRTL-5 cells, in mice and in humans. In FRTL-5 cells, theophylline increased the uptake of radioactive iodine and intracellular cAMP only at low concentrations (1 microM). In mice, theophylline increased slightly the radioiodine uptake, although this increase varied from 1.5- to 6.6-fold. In humans, theophylline decreased slightly the radioiodine uptake, a decrease that became more pronounced with time after radioiodine administration. These studies suggest that theophylline modulates the radioiodine uptake in a dose-dependent fashion, although the modulation is mild and probably not applicable to the clinical setting.
authors.affiliation: Department of Pathology, The Hopkins Medical Institutions, 720 Rutland Avenue, Baltimore, MD 21205, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Lee
authors.forename: R L
authors.initials: RL
authors.lastname: Zemans
authors.forename: M
authors.initials: M
authors.lastname: Hejazi
authors.forename: B B
authors.initials: BB
authors.lastname: Chin
authors.forename: P W
authors.initials: PW
authors.lastname: Ladenson
authors.forename: P
authors.initials: P
authors.lastname: Caturegli
mesh_terms: D000328:Adult; D000818:Animals; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D005260:Female; D006801:Humans; D007454:Iodides / Q000378:metabolism*; D007457:Iodine Radioisotopes; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D011877:Radionuclide Imaging; D013806:Theophylline / Q000494:pharmacology*; D013961:Thyroid Gland / Q000166:cytology / Q000000981:diagnostic imaging* / Q000378:metabolism*
chemical_list: D007454:Iodides; D007457:Iodine Radioisotopes; D010726:Phosphodiesterase Inhibitors; D013806:Theophylline; D000242:Cyclic AMP