Endocrine Abstracts

Introduction: Saliva is an interesting alternative to blood in clinical evaluation of endocrine function. Certain advantages of saliva collection must be considered, when comparing with conventional blood sampling. Vital arguments are that procedure is easy, non-invasive and stress-free. The studies on correlation between salivary and serum thyroid hormones are scarce and contradictory. The goal of our research was to assess if salivary thyroid hormone levels reflect serum concentration.

Methods: This is a prospective study with a consecutive enrollment of patients routinely referred for thyroid hormone’s evaluation. We recruited 109 patients with various thyroid disorders. We assessed TSH, ft3 and ft4 concentration in serum with electrochemiluminescence (ECLIA) immunoassays and chemiluminescence immunoassay (CLIA). Serum levels of anti-thyroid antibodies were measure with ECLIA. In saliva, ft3 and ft4 levels were evaluated by the liquid chromatography with tandem mass spectrometry (LC-MS/MS) analytical technique. Venous blood samples were collected in the morning, after an overnight fast. Saliva samples were obtained in the morning into special Salivette® tubes. Saliva was picked up after at least 30 minutes of eating, drinking, smoking, or chewing gum.

Results: There was a consistency between ECLIA and CLIA methods for serum assessment of TSH, ft3 and ft4. In the whole group (P<0.001, R 0.575) and in the subgroup with TSH within reference interval (P<0.001, R 0.570) salivary ft3 and ft4 were positively correlated. Then we evaluated correlation between serum and salivary hormone concentrations, according to TSH reference ranges. Serum ft4 correlated positively with salivary ft4 in entire group (ECLIA P<0.001, R 0.355; CLIA P<0.001, R 0.384), in subgroup with TSH within reference interval (ECLIA P=0.027, R 0.256; CLIA P<0.001, R 0.263) and in one with TSH above normal limit (CLIA P=0.014, R 0.712). Adversely, serum ft3 correlated with salivary hormone only in patient with TSH below normal value (CLIA P=0.017, R -0.802; ECLIA P=0.011, R -0.826). Then we assess how levothyroxine therapy for hypothyroidism influence serum/saliva thyroid hormones correlations. Salivary and serum hormones were correlated only in naïve treatment patients. We evaluated also if anti-thyroid antibodies have an impact on salivary and serum thyroid hormones.

Conclusions: Our study indicated that salivary thyroid hormones to a certain degree mirror levels of their serum equivalents. Even, in patients with anti-thyroid antibodies, but not on levothyroxine treatment, saliva assessment may be of clinical value. Our research provide a basis for future studies concerning usefulness of saliva in evaluation of thyroid function.