Why You Might Not Be Growing Part 2


Participants completed the visual analog scales for global vigor and global affect at 2-hour intervals each day. Comparisons between conditions were performed using 2-sided nonparametric Wilcoxon tests with a significance level of .05. The 10 healthy men had a mean (SD) age of 24.3 (4.3) years and a mean (SD) body mass index of 23.5 (2.4) (calculated as weight in kilograms divided by height in meters squared). Total (SD) sleep time decreased from 8 hours 55 minutes (35 min) to 4 hours 48 minutes (6 min) with sleep restriction (P = .002). Relative to the rested condition, during each restricted night, participants lost a total (SD) of 2 hours 45 minutes (29 min) of stage-2 sleep (P = .002) and 1 hour 3 minutes (18 min) of REM sleep (P = .002) and gained 9 minutes (8 min) of sleep in stages 3 + 4 (P = .01). During waking hours common to both conditions (8 AM-10 PM), testosterone levels were lower after sleep restriction than in the rested condition (16.5 [2.8] nmol/L vs 18.4 [3.8] nmol/L; P = .049). The effect of restricted sleep was especially apparent between 2 PM and 10 PM (15.5 [3.1] nmol/L vs 17.9 [4.0] nmol/L; P = .02). Daytime cortisol profiles were similar under both conditions. Daily sleep restriction was associated with a progressive decrease in mean (SD) vigor scores from 28 (5) after the first night to 19 (7) after the seventh night (P = .002).  Shown are mean values. In the rested condition, bedtimes were from 10 PM to 8 AM. Values for partial sleep restriction were taken after 1 week of restriction, for which bedtimes were from 12:30 AM to 5:30 AM. On average over the 68 time points, the SD of testosterone levels at each time point was 5.01 nmol/L (range, 2.98-7.53 nmol/L) in the rested condition and 4.26 nmol/L (range, 2.82-6.92 nmol/L) in the restricted condition. On average over the 68 time points, the SD of cortisol levels at each time point was 67.1 nmol/L (range, 15.2-142.7 nmol/L) in the rested condition and 54.0 nmol/L (range, 7.7-162.3 nmol/L) in the restricted condition (2.)

In close relation is a study on sleep deprivation and how it reduces circulating androgens in healthy men. “The acute effect of sleep deprivation on the pituitary-testis axis was evaluated in 13 healthy men. To study such association, the circulating levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), Androstenedione (A), Testosterone (T), Dihydro-testosterone (DHT) and Estradiol (E2) were measured along with Cortisol (C) before and after sleep deprivation. Morning (8:00 AM) venous blood samples were obtained prior and after a continuous restless period of 24 hr and the values were analyzed by the paired Student’s t test. There was a significant and parallel decrease of each androgen and E2 but not of FSH, L.H. PRL, or C, associated with the acute sleep deprivation” (3.) The issues that we are seeing tie directly into cortisol. The issue that arises is that coristol usually pulsates in pattern (meaning its higher in the morning and lower at night) BUT when sleep is deprived, it essentially disrupts this pattern and there by increases serum cortisol levels. Leproult shows this very well in a study from 1997. Sleep curtailment constitutes an increasingly common condition in industrialized societies and is thought to affect mood and performance rather than physiological functions. There is no evidence for prolonged or delayed effects of sleep loss on the hypothalamo-pituitary-adrenal (HPA) axis. We evaluated the effects of acute partial or total sleep deprivation on the nighttime and daytime profile of cortisol levels. Plasma cortisol profiles were determined during a 32-hour period (from 1800 hours on day 1 until 0200 hours on day 3) in normal young men submitted to three different protocols: normal sleep schedule (2300-0700 hours), partial sleep deprivation (0400-0800 hours), and total sleep deprivation. Alterations in cortisol levels could only be demonstrated in the evening following the night of sleep deprivation. After normal sleep, plasma cortisol levels over the 1800-2300-hour period were similar on days 1 and 2. After partial and total sleep deprivation, plasma cortisol levels over the 1800-2300-hour period were higher on day 2 than on day 1 (37 and 45% increases, p = 0.03 and 0.003, respectively), and the onset of the quiescent period of cortisol secretion was delayed by at least 1 hour. We conclude that even partial acute sleep loss delays the recovery of the HPA from early morning circadian stimulation and is thus likely to involve an alteration in negative glucocorticoid feedback regulation. Sleep loss could thus affect the resiliency of the stress response and may accelerate the development of metabolic and cognitive consequences of glucocorticoid excess (4.)


  1. Acute partial sleep deprivation increases food intake in healthy men. Laurent Brondel, Michael A. Romer, Pauline M. Nougues, Peio Touyarou, Damien Davenne. Am J Clin Nutr. 2010 (https://www.ncbi.nlm.nih.gov/pubmed/20357041)
  2. Effect of 1 Week of Sleep Restriction on Testosterone Levels in Young Healthy Men. Leproult, R., & Van Cauter, E. (2011). (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4445839/)
  3. Sleep deprivation reduces circulating androgens in healthy men. V. Cortés-Gallegos, G. Castañeda, R. Alonso, I. Sojo, A. Carranco, C. Cervantes, A. Parra. Arch Androl. 1983 (https://www.ncbi.nlm.nih.gov/pubmed/6405703)
  4. Sleep loss results in an elevation of cortisol levels the next evening. R. Leproult, G. Copinschi, O. Buxton, E. Van Cauter. Sleep. 1997 (https://www.ncbi.nlm.nih.gov/pubmed/9415946)
  5. Sleep disturbances are correlated with decreased morning awakening salivary cortisol. Jutta Backhaus, Klaus Junghanns, Fritz Hohagen. Psychoneuroendocrinology. 2004 (https://www.ncbi.nlm.nih.gov/pubmed/15219642)
  6. Growth hormone secretion during sleep. Y. Takahashi, D. M. Kipnis, W. H. Daughaday. J Clin Invest. 1968 (https://www.ncbi.nlm.nih.gov/pubmed/5675428)
  7. Effect of sleep deprivation on overall 24 h growth-hormone secretion. G. Brandenberger, C. Gronfier, F. Chapotot, C. Simon, F. Piquard. Lancet. 2000 (https://www.ncbi.nlm.nih.gov/pubmed/11052586)
  8. Influence of partial sleep deprivation on energy balance and insulin sensitivity in healthy women. Anja Bosy-Westphal, Silvia Hinrichs, Kamila Jauch-Chara, Britta Hitze, Wiebke Later, Britta Wilms, Uta Settler, Achim Peters, Dieter Kiosz, Manfred James Muller. Obes Facts. 2008 (https://www.ncbi.nlm.nih.gov/pubmed/20054188)
  9. Optimism and self-esteem are related to sleep. Results from a large community-based sample. Sakari Lemola, Katri Räikkönen, Veronica Gomez, Mathias Allemand. Int J Behav Med. 2013 (https://www.ncbi.nlm.nih.gov/pubmed/23055029)
  10. Sleep duration and cardiometabolic risk: a review of the epidemiologic evidence. Kristen L. Knutson. Best Pract Res Clin Endocrinol Metab. (https://www.ncbi.nlm.nih.gov/pubmed/21112022)