This paper proposes that the renal protective mechanism of GLP-1 receptor agonists, including semaglutide, is selenium-gated: GLP-1-mediated NRF2 activation drives selenoprotein gene transcription that cannot be translated into functional enzymes without adequate selenocysteine substrate. An August 2025 Redox Biology paper (Arisawa et al.) confirmed that NRF2-dependent transcription suppresses SELENOP expression, potentially reducing peripheral selenium delivery while upregulating intracellular selenoprotein demand. The bone health addendum documents that osteoblast selenoproteins GPx1 and TrxR1 are subject to the same mechanism, and that vitamin D bone protection is partially selenium-gated through TrxR1 activation. Clinical monitoring recommendations for GLP-1 users include baseline SELENOP and GPx activity alongside standard DXA scanning. All claims are hypothesis-level.