T3 may be a better agent than T4 in the critically ill hypothyroid patient: evaluation of transport across the blood-brain barrier in a primate model

Journal Article · Tue Feb 01 00:00:00 EST 1983 · Crit. Care Med.; (United States)

DOI:https://doi.org/10.1097/00003246-198302000-00009· OSTI ID:6191677

Chernow, B; Burman, K D; Johnson, D L; McGuire, R A; O'Brian, J T; Wartofsky, L; Georges, L P

Thyroid hormone transport across the blood brain barrier in hypothyroid patients is clinically important yet poorly understood. To study this question, 200 micrograms of thyroxine (T4), 100 micrograms of 3,5,3'-triiodothyronine (T3) and 100 micrograms of 3,3',5'-triiodothyronine (reverse T3) were administered separately to 3 baboons, first iv and at a later date intrathecally (IT). Six animals were used. Three received the iv injections and three received the IT injections. In each of the 18 experiments, cerebrospinal fluid (CSF) and serum specimens were collected serially for 6 h after injection. Mean maximal elevations from baseline in CSF iodothyronine levels were 100 +/- 10 ng/dl after iv T4, 3921 +/- 293 ng/dl after iv T3 and 31 +/- 17 ng/dl after iv reverse T3. When given IT in the same dosages, the mean maximal increases in serum iodothyronine concentrations were: 1670 +/- 600 ng/dl for T4, 806 +/- 405 ng/dl for T3, and 210 +/- 43 ng/dl for reverse T3. In every animal studied, rapid bidirectional transfer of T3 from serum to CSF and CSF to serum occurred, whereas iv T4 resulted in delayed minimal increments in CSF T4 concentration. Isotopic experiments were also performed and the results analyzed using a kinetic model. When /sup 125/I-T3 was given iv, the equilibrium point in CSF was observed within 90 min with 1.7% of the administered dose/L able to be counted in CSF at any moment in time. When labeled T4 was given iv, only 0.6% of the administered dose/L was counted in CSF and the equilibrium point was not reached until 360 min. These data suggest: T4, T3, and reverse T3 are all capable of bidirectional transfer across the blood brain barrier, T3 may be a better agent than T4 in treating patients with myxedema coma because T3 crosses more rapidly and more completely from serum to CSF.

• Research Organization: Department of Medicine and Neurosurgery, National Naval Medical Center, Bethesda, MD
• OSTI ID: 6191677
• Journal Information: Crit. Care Med.; (United States), Vol. 11:2, Issue 2
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
59 BASIC BIOLOGICAL SCIENCES
BLOOD-BRAIN BARRIER
MEMBRANE TRANSPORT
THYROXINE
TRIIODOTHYRONINE
ANIMALS
BIOLOGICAL MODELS
COMPARATIVE EVALUATIONS
HYPOTHYROIDISM
IODINE 125
PATIENTS
PHYSIOLOGY
TRACER TECHNIQUES
AMINO ACIDS
BETA DECAY RADIOISOTOPES
CARBOXYLIC ACIDS
DAYS LIVING RADIOISOTOPES
DISEASES
ELECTRON CAPTURE RADIOISOTOPES
ENDOCRINE DISEASES
HORMONES
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC IODINE COMPOUNDS
PEPTIDE HORMONES
RADIOISOTOPES
THYROID HORMONES
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