Sleep is important for healthy testosterone production, and sadly low testosterone levels can cause insomnia and sleep disturbance, creating a cyclular issue. Meaning that treating one issue can help improve the other and ignoring one can in turn make matters worse.
It's been shown that even cutting sleep slightly short having 5 hours instead of 6 or 7 can result in testosterone levels of up to 15% lower (we'll talk more about the studies later).
There are also secondary effects of poor sleep that can lower testosterone levels, such as increased cortisol resulting in testosterone disruption, or weight gain as a result of increased ghrelin (the hunger hormone) from not getting enough sleep.
Testosterone Production and Sleep
Plasma testosterone levels have fluctuations throughout the day, with peak levels occurring during sleep and dropping off by the late afternoon. This increase in testosterone is sleep-dependent and requires a minimum of three hours of uninterrupted sleep. The first REM sleep episode correlates with the peak levels of testosterone, emphasizing the importance of quality sleep in testosterone production. 
Sleep Disorders and Testosterone
Various sleep disorders can disrupt the normal sleep patterns and have a detrimental effect on testosterone levels. Sleep deprivation, characterized by inadequate sleep duration, has been shown to decrease testosterone levels significantly. In one study men who slept less than five hours a night for one week experienced a substantial decrease in testosterone levels compared to when they had a full night's sleep. The impact of sleep deprivation on testosterone levels is equivalent to aging 10 to 15 years. 
Sleep Restriction and Testosterone Levels
Short-term sleep restriction has been found to have a serious and notable impact on testosterone levels. In the aforementioned study, young men who slept for less than five hours experienced a decrease of 10% to 15% in testosterone levels. The effect of sleep restriction on testosterone was noticeable after just one week of inadequate sleep. Interestingly, the lowest testosterone levels were observed in the afternoons of sleep-restricted days, between 2 pm and 10 pm. This has been replicated in other studies with relatively similar results. 
The Consequences of Low Testosterone Levels
Low testosterone levels can have wide ranging implications for men's health and well-being. Testosterone is essential for the development and maintenance of muscle mass, bone density, and sexual function not to mention mood and the mental issues it can cause. When testosterone levels are compromised, individuals may experience reduced energy levels, decreased libido, poor concentration, and fatigue. 
Sleep Disorders and Testosterone Levels
Sleep Quality and Testosterone
Not only sleep duration but also sleep quality plays a crucial role in testosterone regulation. Abnormalities in sleep quality, such as waking up frequentl or even mild disturbances if they're preventing a full REM cycle, can result in decreased testosterone levels. Sleep disordered breathing, including conditions like sleep apnea, may also contribute to reduced testosterone levels. The presence of upper airway resistance during sleep can lead to snoring and, in severe cases, obstructive sleep apnea, which has been shown to lower testosterone levels. While the exact mechanisms behind the relationship between sleep quality and testosterone levels are still being researched, it is clear that maintaining healthy sleep patterns is fundamental for optimal testosterone production. 
Shift Work and Testosterone
Shift work, characterized by working outside of standard daytime hours, can disrupt the natural sleep-wake cycle and have adverse effects on testosterone levels. Studies have shown that individuals engaged in shift work, particularly night shifts, experience alterations in sleep patterns and a subsequent decrease in testosterone levels. The impact of shift work on testosterone appears to be mediated by the disruption of circadian rhythms, which play a crucial role in regulating hormone production. 
Treatment and Prevention of Sleep-Related Testosterone Issues
Addressing Sleep Disorders
Recognizing the importance of sleep in testosterone regulation, it is vital to address and treat sleep disorders to maintain optimal hormone levels. For individuals with sleep apnea, continuous positive airway pressure (CPAP) therapy is a common treatment option. By ensuring uninterrupted airflow during sleep, CPAP therapy can help alleviate the effects of sleep apnea on testosterone levels.  Additionally, improving sleep hygiene, such as maintaining a regular sleep schedule and creating a conducive sleep environment, can positively impact sleep quality and subsequently testosterone production.
In addition to addressing sleep disorders, certain lifestyle modifications can help optimize testosterone levels. Regular exercise, particularly resistance training, has been shown to increase testosterone levels in men. Adequate nutrition, including a balanced diet rich in essential nutrients, is also crucial for hormone regulation. Maintaining a healthy weight, avoiding excessive alcohol consumption, and managing stress levels are additional lifestyle factors that can positively influence testosterone levels.
Is Sleep Important For Testosterone?
In short, sleep plays a vital role in testosterone regulation in men. Sleep deprivation and sleep disorders can significantly impact testosterone levels, leading to a range of adverse health effects. By prioritizing quality sleep and addressing any underlying sleep disorders, individuals can take proactive steps towards optimizing their testosterone levels and improving their overall health.
1 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3955336/
2 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4445839/
3 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6917985/
4 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4391003/
5 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8350060/
6 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7484090/
7 - https://www.nhlbi.nih.gov/health/cpap