Acute decrease in plasma testosterone and appetite after either glucose or protein beverages in adolescent males

Quantifying the variability in the assessment of reproductive hormone levels

OBJECTIVE

To quantify how representative a single measure of reproductive hormone level is of the daily hormonal profile using data from detailed hormonal sampling in the saline placebo-treated arm conducted over several hours.

DESIGN

Retrospective analysis of data from previous interventional research studies evaluating reproductive hormones.

SETTING

Clinical Research Facility at a tertiary reproductive endocrinology centre at Imperial College Hospital NHS Foundation Trust.

PATIENTS

Overall, 266 individuals, including healthy men and women (n = 142) and those with reproductive disorders and states (n = 124 [11 with functional hypothalamic amenorrhoea, 6 with polycystic ovary syndrome, 62 women and 32 men with hypoactive sexual desire disorder, and 13 postmenopausal women]), were included in the analysis.

INTERVENTIONS

Data from 266 individuals who had undergone detailed hormonal sampling in the saline placebo-treated arms of previous research studies was used to quantify the variability in reproductive hormones because of pulsatile secretion, diurnal variation, and feeding using coefficient of variation (CV) and entropy.

MAIN OUTCOME MEASURES

The ability of a single measure of reproductive hormone level to quantify the variability in reproductive hormone levels because of pulsatile secretion, diurnal variation, and nutrient intake.

RESULTS

The initial morning value of reproductive hormone levels was typically higher than the mean value throughout the day (percentage decrease from initial morning measure to daily mean: luteinizing hormone level 18.4%, follicle-stimulating hormone level 9.7%, testosterone level 9.2%, and estradiol level 2.1%). Luteinizing hormone level was the most variable (CV 28%), followed by sex-steroid hormone levels (testosterone level 12% and estradiol level 13%), whereas follicle-stimulating hormone level was the least variable reproductive hormone (CV 8%). In healthy men, testosterone levels fell between 9:00 am and 5:00 pm by 14.9% (95% confidence interval 4.2, 25.5%), although morning levels correlated with (and could be predicted from) late afternoon levels in the same individual (r2 = 0.53, P<.0001). Testosterone levels were reduced more after a mixed meal (by 34.3%) than during ad libitum feeding (9.5%), after an oral glucose load (6.0%), or an intravenous glucose load (7.4%).

CONCLUSION

Quantification of the variability of a single measure of reproductive hormone levels informs the reliability of reproductive hormone assessment.

Oral 3-hydroxybuturate ingestion acutely lowers circulating testosterone concentrations in healthy young males

Ketone bodies, such as 3-hydroxybutyrate (3-OHB), have been frequently used by endurance athletes, such as cyclists, to enhance performance and recovery and are recognized for their health benefits and therapeutic effects for decades. Testosterone is a potent regulator of red blood cell production. Evidence suggests that ketone bodies can increase the production of erythropoietin, which stimulates red blood cell production. Therefore, we investigated whether an acute increase in 3-OHB levels affects testosterone levels in healthy young men. We studied six healthy, young male participants who fasted overnight and were tested twice: (i) after drinking 37.5 g of Na-D/L-3-OHB dissolved in 500 mL of distilled water (KET), and (ii) after drinking 500 mL of placebo saline water (0.9% NaCl) (CTR). During the KET trial, 3-OHB levels increased to approximately 2.5 mM. Testosterone levels decreased significantly by 20% during KET compared to 3% during CTR. A simultaneous increase in luteinizing hormone was observed in KET. We observed no changes in other adrenal androgens, such as androstenedione and 11-keto androgens. In conclusion, an acute increase in 3-OHB levels decreases testosterone levels. Concomitantly, an increase in luteinizing hormone was observed. This suggests that 3-OHB may counteract some of the beneficial effects of endurance training. Further studies, involving larger sample sizes and performance outcomes, are required to fully understand this phenomenon.

Protein supplement consumption prevalence, habits and complications in adolescents

INTRODUCTION

The consumption of nutritional and protein supplements by adolescents may have important consequences for their health.

METHODS

Prospective observational study based on a survey of adolescents enrolled in 6 schools selected at random in the city of Seville. Our primary objective was to determine the actual consumption of dietary supplements in the adolescent population and quantifying their protein content.

RESULTS

We obtained a total of 263 valid responses that showed a prevalence of consumption of nutritional supplements of any kind of 19.01%, of which 56.0% (10.64% of the total) corresponded to adolescents that consumed protein supplements for a mean protein intake of 0.26 g/kg/day (SD, 0.18). The profile of consumers of any type of supplements differed from that of nonconsumers in age, use of long-term medication and weight loss or high-protein diets. The comparison of adolescents who consumed protein supplements versus nonprotein supplements only evinced a significant difference in the control of supplement consumption. Although most of these adolescents were not subject to external control, 25.92% of those who consumed protein supplements were monitored by a professional, compared to 7.38% of consumers of nonprotein supplements. In the group that consumed protein supplements, 85.18% of adolescents achieved the desired effect and 18.51% reported some form of negative effect.

CONCLUSIONS

The prevalence of protein supplement consumption among adolescents in our area is 10.64%, with consumption of amounts corresponding to 25% of the recommended daily allowance of protein. The profile of protein supplement consumers is very similar to that of nonprotein supplement consumers.