Acute beta-blockade changes the extracellular distribution of thyroid hormones.
The acute (within hours) changes in the concentrations of T4, T3, reverse-T3 (rT3) and T3 resin uptake test (T3RU) were studied in 31 hyperthyroid patients for 4 h after po treatment with either acebutolol, oxprenolol, pindolol or timolol. In 21 of the patients, the changes were compared to changes in the serum concentrations of alpha 2-macroglobulin (a macromolecule) and two middle-sized molecules; thyroid hormone-binding globulin (TBG) and albumin in order to calculate the changes in extracellular distribution of the thyroid hormones and to distinguish between changes due to a changed metabolism and changes due to a changed distribution of the thyroid hormones. Acebutolol, oxprenolol and timolol caused a decrease in serum T3 after 1/2 h, and acebutolol and oxprenolol also a decrease in rT3 after 1/2 - 1 h, the changes reversed within 2 h. A concomitant decrease in serum albumin and TBG suggests a change in the extracellular distribution of middle-sized molecules to which thyroid hormones are attached, as an explanation of the acute decrease (1 h) of the thyroid hormones. The small and insignificant change in alpha 2-macroglobulin indicates that the changes are mainly extravascular, but the difference of alpha 2-macroglobulin changes between the drugs (acebutolol/timolol vs pindolol/oxprenolol) could depend on the intrinsic sympathomimetic activity of the drugs.
Department of Internal Medicine and Endocrinology F, Herlev hospital, Denmark.
L
L
Kayser
H
H
Perrild
P H
PH
Petersen
L
L
Skovsted
J E
JE
Hansen
D000070:Acebutolol / Q000493:pharmacokinetics / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000493:pharmacokinetics / Q000494:pharmacology*; D000328:Adult; D002352:Carrier Proteins / Q000097:blood; D005260:Female; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000097:blood; D008875:Middle Aged; D010096:Oxprenolol / Q000493:pharmacokinetics / Q000494:pharmacology; D010869:Pindolol / Q000493:pharmacokinetics / Q000494:pharmacology; D012709:Serum Albumin / Q000032:analysis; D013963:Thyroid Hormones / Q000097:blood*; D013974:Thyroxine / Q000097:blood; D013999:Timolol / Q000493:pharmacokinetics / Q000494:pharmacology; D014018:Tissue Distribution; D014284:Triiodothyronine / Q000097:blood; D000511:alpha-Macroglobulins / Q000032:analysis; D000097810:Thyroid Hormone-Binding Proteins
D000070:Acebutolol; D000319:Adrenergic beta-Antagonists; D002352:Carrier Proteins; D008565:Membrane Proteins; D010096:Oxprenolol; D010869:Pindolol; D012709:Serum Albumin; D013963:Thyroid Hormones; D013974:Thyroxine; D013999:Timolol; D014284:Triiodothyronine; D000511:alpha-Macroglobulins; D000097810:Thyroid Hormone-Binding Proteins