33p5p-Triiodo-L-thyronine (CAS 5817-39-0) is a thyroid hormone metabolite that acts primarily in the cytoplasm by activating a truncated thyroid receptor form (TR 1) which lacks nuclear localization capability It modulates cytoplasmic thyroid hormone receptor pathways and contributes to actin filament polymerization in neuronal and astrocytic cell populations 33p5p-Triiodo-L-thyronine exhibits its biological effects through non-classical signaling mechanisms In primary cultures of neuronal and astrocytic models it induces cytoskeletal remodeling events such as actin polymerization Based on these pharmacological properties 33p5p-Triiodo-L-thyronine serves as a research tool in neuroscience and endocrine studies focused on cytoplasmic thyroid hormone signaling and cellular morphology