Correlation of plasma and salivary oxytocin in healthy young men - experimental evidence.

OBJECTIVES: The neuroactive hormone oxytocin (OT) has significant influence on human behavior, and it has been measured peripherally in venous blood and in saliva in many behavioral neuroscience studies. Assessment of salivary hormone levels is popular due to non-invasiveness, but there is a controversy as to whether OT can be reliably measured in saliva and how possible time lags between plasma and salivary OT levels influence correlation. DESIGN AND METHODS: In order to shed light on the question whether salivary and plasma OT levels correlate, we designed an experiment where healthy young men had to look at a presentation of trustworthy faces on a computer screen (faces were taken from an established database in trust research). During three points in time, plasma and saliva samples were collected and analyzed using ELISA. RESULTS: Plasma and salivary OT levels did not correlate even when considering a time lag of 15 or 30 minutes. CONCLUSIONS: Our results suggest that plasma and salivary OT levels do not correlate in healthy young men, and hence comparison of results across plasma and salivary studies is neither informative nor warranted. However, we recommend replicating this study based on mixed-gender samples.

Hyperthyroidism affects arterial stiffness, plasma NT-pro-B-type natriuretic peptide levels, and subendocardial perfusion in patients with Graves' disease.

BACKGROUND: Arterial stiffness is thought to play a critical role in the pathogenesis of cardiovascular events, and in hyperthyroidism increased cardiovascular event rates have been reported. AIM: To investigate markers of systemic arterial stiffness, volume homeostasis, and subendocardial perfusion and its interrelationship in patients with Graves' disease (GD) in hyperthyroidism and euthyroidism. METHOD: Aortic augmentation index (AIx@75) as a measure of systemic arterial stiffness and subendocardial viability ratio (SEVR) as a surrogate measure of subendocardial perfusion were assessed by applanation tonometry in 59 patients with GD in hyperthyroidism and euthyroidism, and measurements were compared to plasma levels of NT-pro-B-type natriuretic peptide (NT-ProBNP). RESULTS: AIx@75 and NT-ProBNP levels were significantly increased in hyperthyroidism compared to euthyroidism and were positively correlated with each other. SEVR was significantly decreased in hyperthyroidism compared to euthyroidism, mainly due to increased heart rates as shown by the heart rate-corrected SEVR75. CONCLUSIONS: In hyperthyroidism, patients with GD exhibited increased systemic arterial stiffness, paralleled by increased levels of NT-ProBNP, a marker of volume overload. The decreased subendocardial perfusion in hyperthyroidism seemed to be mainly due to increased heart rates. The observed unfavorable hemodynamic alterations in hyperthyroidism may serve to explain increased cardiovascular event rates in patients with GD.