As part of a study on tissue uptake of thyroxine (T4) in a transthyretin (TTR)-null mouse strain, kinetic parameters of thyroxine metabolism in wild-type mice under normal physiological conditions are presented. Kinetic analysis of injected [(125)I]T4 showed that TTR-null mutants have markedly increased [(125)I]T4 transfer rate constants from plasma to the fast-exchange compartments of liver and kidney and from fast to slow kidney compartments. Transfer rates from plasma to brain, testes, and fat were little affected. The T4 tissue content in the mutants was greatly reduced in brain but relatively normal in liver and kidney. No major changes were observed in brain 3,3',5-triiodothyronine concentrations, suggesting that availability of this hormone is not markedly altered in the mutant mice. The low T4 brain content probably reflects the absence of T4-TTR complexes in the mutant choroid plexus and cerebrospinal fluid. This study indicates that TTR is not essential for T4 tissue uptake or for T4 to reach the brain across the choroid plexus-cerebrospinal fluid and/or blood-brain barriers.
Leptomeningeal carcinomatosis is characterized by multifocal seeding of the meninges by malignant tumor cells. It is a rare and generally manifests in advanced stage of solid tumors, being most common in breast and lung cancer. In the pancreatic cancer, the spread to the leptomeninges is extremely rare, although it can become an increasingly common affectation if the overall survival of these patients increases. The clinical presentation is non-specific, but usually neurological symptoms, and diagnosis includes MRI and cerebrospinal fluid cytology. Below, we present a case of a patient diagnosed with pancreatic adenocarcinoma of more than one year´s evolution who develops meningeal carcinomatosis.
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