When people colloquially speak of the “days of the month” for men, they are not referring to weekly or monthly fluctuations like those that occur in women. Instead, it refers to the diurnal fluctuations in men’s testosterone levels, which rise and fall throughout the day. It was definitively established in the so-called Mars-500 observational study in 2012 that male hormones also follow cycles. A hormonal cycle in men was observed with the steroid hormone aldosterone (a 28-day cycle). However, the data only allowed for conjectures about a 7- or 14-day cycle for the hormones testosterone and cortisol (Rakova et al., 2013).
In addition to natural fluctuations throughout the day, however, testosterone levels can also fall or fluctuate due to age, lifestyle factors, and co-morbidities. These fluctuations can have a significant impact on men’s physical and mental health. In this article, we examine the causes and effects of these fluctuations, as well as their significance for the diagnosis of testosterone levels, to enable a more comprehensive understanding of this important hormone.
Causes of Testosterone Fluctuations
Testosterone fluctuations can be caused not only by the so-called “circadian rhythm” throughout the day, but also by aging, lifestyle factors, and co-morbidities. These fluctuations can have a significant impact on men’s physical and mental health.
Diurnal Fluctuations Caused by the Circadian Rhythm
As mentioned, the male testosterone cycle is time-dependent. Testosterone levels are generally higher in the morning and decrease throughout the day (Brambilla et al., 2009). This daily pattern, known as the circadian rhythm, must also be taken into account when planning blood tests to obtain consistent and comparable results. The diurnal fluctuations caused by this bodily rhythm actually lead to relevant differences in testosterone levels. In the evening, the same test subjects had testosterone levels up to 12.9% lower. This fluctuation is referred to as intra-individual biological variation throughout the day. A study by Collier et al. (2010) showed that serum testosterone levels were 1.5 nmol/L (43 ng/dL) lower in the afternoon than in the morning.
The time of day is therefore a very relevant factor for the level of testosterone. For this reason, blood testosterone measurements should always be taken at the same time in the morning to ensure better comparability.
The Influence of Lifestyle
In addition, these natural fluctuations throughout the day can be further influenced by sleep patterns, diet, and physical activity. For example, the intra-individual biological variation in morning serum testosterone between different days was as high as 18.7%, which is even greater than that caused solely by the time of day. This is where lifestyle habits such as chronic stress, sleep deprivation, lack of exercise, and the consumption of harmful substances like alcohol come into play (Collier et al., 2010).
Stress: Stress is a major factor that can also have a lasting impact on testosterone levels. Chronic stress leads to the release of cortisol, a stress hormone that can inhibit the production and release of testosterone. Therefore, reducing stress through techniques such as meditation, yoga, or simply regular rest and relaxation can have a positive effect on testosterone levels (Xiong et al., 2021). Acute stress also has a direct impact on testosterone levels, with short-term increases also observed alongside cortisol. It is suspected that testosterone plays an adaptive role in conjunction with cortisol during acute stress phases (Zueger et al., 2023).
Sleep: Furthermore, poor sleep quality can negatively affect testosterone levels. Regular, sufficient, and high-quality sleep is essential for maintaining a healthy hormonal balance. Research shows that sleep deprivation, especially the reduction of REM sleep phases, can lead to a significant decrease in testosterone levels (Agrawal et al., 2022).It has even been shown that an acoustic sound that impairs sleep quality can lower morning testosterone levels. So even one night of poor sleep can have a negative effect on testosterone levels in the short term (Ukraintseva et al., 2018).
Exercise: During endurance sports and strength training, testosterone levels rise, often for some time after the workout before settling again. The long-term effects of exercise on testosterone levels are presumably caused primarily by weight loss (Riachy et al., 2020).
Alcohol consumption: Studies have repeatedly shown that excessive alcohol consumption has a lasting negative impact on testosterone levels (Smith et al., 2023). Chronic alcohol consumption is thought to inhibit the hormonal axis in healthy men. However, the exact mechanisms that explain the link between alcohol consumption and impaired steroidogenesis are not yet fully known (Santi et al., 2023).
Co-morbidities
In addition to the factors already mentioned, certain co-morbidities can also lead to low testosterone levels. There is a particularly strong link between type II diabetes, metabolic syndrome, and testosterone deficiency—therefore, testosterone levels should be monitored closely in these patients (Traish et al., 2011). In our expert blog post “Why Diabetics Should Keep a Close Eye on Their Testosterone Levels,” you can read more details on this topic.
Age-Related Testosterone Decline
Testosterone levels in men decline with age. This age-related testosterone decline usually begins between the ages of 35 and 55 (Matsumoto, 2002). During this period of life, men experience a decline in their testosterone levels of approximately 1–2% per year (Stanworth & Jones, 2008).
This decline in testosterone levels is an aging process, similar to menopause in women. However, this so-called “andropause” differs in that the testosterone decline occurs gradually over a longer period. It is therefore not an acute fluctuation in testosterone levels, such as that caused by the circadian rhythm, but rather a long-term development. Regardless, a manifest testosterone deficiency in old age should by no means be considered “normal.” Rather, it is a pathological condition caused by an unhealthy lifestyle and associated co-morbidities. In our expert article “Myths and Facts About Testosterone,” we clarify this myth in detail. You can also learn more about testosterone deficiency in our article: “Testosterone Deficiency in Men: Causes, Symptoms, and Solutions.”
Symptoms of Testosterone Fluctuations
A balanced testosterone level is crucial for men’s health. Testosterone influences numerous physical, mental, and sexual functions. Short-term fluctuations in testosterone levels are normal in many cases, such as the body’s response to short-term stress or exercise. However, chronic changes, such as those caused by persistent sleep problems, chronic stress, or alcohol consumption, can cause a variety of symptoms that can significantly impair well-being and quality of life. A deficiency or imbalance can thus lead to various physical, mental, and sexual symptoms:
- Physical Symptoms: Among the most common physical signs are muscle weakness, weight gain, and reduced bone density. Men may thus notice a decline in physical performance (Wittert et al., 2003).
- Psychological Symptoms: Fatigue, mood swings, depression, and concentration problems can also indicate low testosterone levels. These symptoms can significantly impair quality of life (Wang et al., 2000).
- Sexual Health: Loss of libido and erectile dysfunction are common symptoms of testosterone deficiency. These issues can have negative effects on both personal well-being and intimate relationships (Hintikka et al., 2009).
The Relevance of Fluctuations for Diagnosis
Due to the complexity of hormonal regulation in the body, influenced by numerous factors such as age, time of day, and lifestyle, several things should be considered when determining testosterone levels.
Short-Term Fluctuations
Short-term fluctuations in testosterone levels are particularly important for the timing of sample collection. Since testosterone levels follow a circadian rhythm, as described earlier, the blood sample for determining these levels is normally taken in the early morning when testosterone levels are at their highest (Brambilla et al., 2009). All subsequent tests should ideally be performed at the same time of day to ensure good comparability.
Medium-Term Fluctuations
Medium-term fluctuations, for example due to stress or sleep deprivation, can temporarily alter baseline testosterone levels. A one-time measurement of testosterone levels therefore only provides a snapshot that may not reflect the actual hormonal landscape. Multiple blood tests, on the other hand, provide a dynamic and comprehensive picture of hormonal status and are thus crucial for an accurate diagnosis and subsequent treatment planning. Therefore, in the event of an abnormal initial test result, a second test is always necessary to confirm the diagnosis of hypogonadism (Bassil et al., 2009). In our blog post "You Are Considering Testing Your Testosterone Levels: That Is Why You Need Multiple Blood Tests," you will find further information on this topic.
Long-Term Fluctuations
As mentioned earlier, both an unhealthy lifestyle, co-existing medical conditions, and age can lead to a long-term lower testosterone level, even to manifest deficiency. This is relevant because many men do not suspect they are affected by testosterone deficiency, especially if it develops gradually and symptoms are interpreted as signs of aging. Therefore, it makes sense to have your testosterone level determined if you experience symptoms that could indicate a deficiency, so that a deficiency can be ruled out or treated if necessary (Traish et al., 2011).
Our Conclusion, Your Knowledge
Fluctuations in testosterone levels can be caused by various factors such as the circadian rhythm, age, lifestyle, and co-existing medical conditions. These fluctuations have far-reaching effects on physical, mental, and sexual health. Accurate diagnosis is crucial to identify the cause of symptoms and take appropriate measures. Testosterone levels should always be measured while taking natural fluctuations and individual differences into account. Multiple blood tests, ideally at the same time of day, are necessary to obtain a comprehensive picture of hormonal status and to make an informed diagnosis.
In conclusion, understanding the highs and lows of testosterone levels is an important foundation for promoting men's health. Through awareness and early diagnosis, men can take proactive steps to support their hormonal balance and sustainably improve their well-being. With this knowledge, we hope to have given you a better understanding of the importance of testosterone levels and their effects on your health. Use this knowledge to actively shape your health and seek professional support if necessary.
