selenomethionine

noun

sel·​e·​no·​me·​thi·​o·​nine -mə-ˈthī-ə-ˌnēn 

: a selenium analog C₅H₁₁NO₂Se of methionine in which sulfur is replaced by selenium and that is used as a diagnostic aid in scintigraphy especially of the pancreas and as a dietary supplement