Salivary Testosterone V1
Research type
Research Study
Full title
Salivary Testosterone in Men: Diurnal Variation and Post-Prandial Responses
IRAS ID
277771
Contact name
Rousseau Gama
Contact email
Sponsor organisation
The Royal Wolverhampton NHS Trust
Clinicaltrials.gov Identifier
Duration of Study in the UK
0 years, 8 months, 31 days
Research summary
Research Summary
This project will investigate whether testosterone in saliva is affected by eating, through a comparison of fasting samples against samples collected after having a sugar drink. This will be beneficial as testosterone in saliva could provide a useful test for diagnosing hypogonadism, which is a disease where testosterone is low in a patient. To test for hypogonadism, research needs to be done to see if salivary testosterone samples should be taken from patients while fasting. This project hopes to answer this question.We will investigate whether the time of day changes salivary testosterone in fasting volunteers. Previous research has shown that testosterone in blood and in saliva is highest in the morning and decreases into the evening. No research has been done on salivary testosterone to see if this relationship is the same in fasting patients. This is important for two reasons. Firstly, we want to check that any changes we might find in salivary testosterone after having a meal, are due to the meal, not just due to the time that has passed. Secondly, it would be interesting to see if salivary testosterone decreases throughout the day due to eating meals, rather than time. This would be explored in volunteers to see if time of day variation is present if the volunteer is fasting, also noting the time period that testosterone starts to decrease significantly in saliva.
Finally, we will be comparing salivary testosterone in fasting against after a meal in patients who are having a glucose tolerance test investigation of diabetes. These patients are an ideal cohort for this study as they are already going through controlled procedures having fasting and 2hr post-meal samples collected, so these patients will be minimally impacted by the study.
Summary of Results
Background:
Testosterone (T) circulates in the blood as biologically active free T (1-2%) but mostly biologically inactive bound T (98-99%) to blood proteins . Blood T, however, is a measurement of free and bound T and in conditions of altered blood protein levels it may be misleading as it does not accurately reflect biologically active serum free T. Testosterone in saliva (Sal T), however, accurately reflects serum free testosterone as it is unbound and in equilibrium with circulating free T. Advantages of Sal T over serum T include a more accurate reflection of circulating biologically active free T, non-invasiveness, reduced stress for the patient (particularly if difficult venous access), no risk of needle stick injury and ease of collection allowing potential home testing and posting of samples. Sal T, therefore, may offer an attractive additional test in investigating disorders of testosterone, particularly in men. Factors, other than testosterone disorders, which affect Sal T require clarification before clinical use of the test.
Blood testosterone levels are reported to be affected by food and subject to diurnal variation (predictable and regular fluctuations in levels during the day). There is limited or no information of the effect of these on Sal T, which these studies intend to address.
Summary of Studies
Effect of oral glucose ingestion on fasting Sal T Salivary and blood samples were collected between 09.00 and 09.30 and two hours after a 75g oral glucose load in 32 men Two hours following oral glucose, there was a decrease in fasting mean (standard deviation) Sal T [178.2 (56.6) vs 146.0 (42.2) pmol/L; p = 0.0003], serum cortisol [332 (105.0) vs 239 (75.3) nmol/L; p = <0.0001] and serum prolactin [193 (75.0) vs 127 (55.9) mIU/L; p = <0.0001] Sal T decreased postprandially. The concomitant decrease in serum cortisol, prolactin and TSH reflecting diurnal variation offers an alternative explanation for the decrease in Sal T independent of food consumption.Diurnal Variations in Sal T
Samples for Sal T were collected in 17 men following an 8h overnight fast at 9am, 10am, and 11am. The participants then broke their fast. Three further Sal T samples were collected following an at least 8h fast at 10pm, 11pm, and 12am following which volunteers broke their fast.
Mean (standard deviation) Sal T concentrations decreased between 9am [191.2 (56.68)] vs 10am [174.2 (53.29)] pmol/L; p = 0.0359], 9am vs 11am [168.1 (52.61)] pmol/L; p = 0.0048], and 9am vs 10pm [120.2 (46.04)] pmol/L; p = 0.0036]. Sal T concentrations at 10pm [120.2 (46.04)] pmol/L], 11pm [130.3 (35.72)] pmol/L, and 12am [125.1 (29.75) pmol/L] were similar (p>0.05).
We confirm Sal T is higher in the morning than evening and report that Sal T decreased stepwise between 9am, 10 am and 11am.Summary of studies
We report that Sal T decreases in the morning independent of food consumption. This may wholly or partly contribute to the decrease in Sal T following oral glucose loading in the morning. These results indicate ithat the optimal Sal T sampling should occur at 9am and further studies are required to determine whether food consumption affects Sal T independent of diurnal variation.REC name
West of Scotland REC 3
REC reference
20/WS/0115
Date of REC Opinion
29 Oct 2020
REC opinion
Further Information Favourable Opinion