Is this text in a database field? (and not text added with the layout text tool)
Is it possible that the text in this field was either pasted from another file/application or was edited by selecting a font size in the formatting tool bar while in browse mode?
If so, the text formatting applied directly to the text in the field supercedes any formatting that you specify for the field on your layout. You'll need to remove the text formatting from the text in the field.