Saliva testing
Saliva is a useful biological fluid for assaying steroid hormones such as cortisol , genetic material like RNA , proteins such as enzymes and antibodies , and a variety of other substances , including natural metabolites , including saliva nitrite , a biomarker for nitric oxide status ( see below for Cardiovascular Disease , Nitric Oxide: a salivary biomarker for cardio-protection ) . 
<triplet> cortisol <subj> steroid hormone <obj> instance of