Waking up in a bed wet with sweat is unpleasant and sometimes disturbing. In athletes, night sweats often have safe explanations: late training, a warm bedroom, alcohol. However, it can also be a marker of overtraining, hormonal failure, side effects of drugs or disease. The editors analyze the mechanisms behind this symptom and where pharmacology has a place in them.
How the body regulates temperature at night
Body temperature has a daily rhythm: it decreases in the evening, and this is one of the signals for falling asleep. In order to "discard" the heat, the blood vessels of the skin expand, and, if necessary, sweating is activated. The center of thermoregulation is located in the hypothalamus and maintains the temperature within a narrow "comfort zone".
When this zone shifts or narrows, the body overreacts: a slight increase in body or environmental temperature causes profuse sweating. This is how hot flushes in menopausal women and men with testosterone deficiency are explained — the decrease in sex hormones makes thermoregulation more unstable.
Doctors distinguish between true night sweats — profuse when you have to change your underwear or bed — and normal sweating from a warm blanket. A systematic review by Mold et al. (2012) points out that in primary care, night sweats are a frequent complaint and in most cases are not associated with serious diseases, but require careful questioning.
For athletes, the situation has its own specificity: intensive training increases basal metabolism and heat production, while diets and supplements actively affect metabolism. Therefore, it is especially important for them to consider pharmacological factors along with general medical ones.
Non-pharmacological causes in athletes
The simplest reason is training late at night. After intense exercise, body temperature and the level of catecholamines remain elevated for several hours, and if a person goes to sleep soon, the body "cools down" already in sleep. A warm bedroom, synthetic underwear and a heavy blanket enhance the effect.
Overtraining syndrome, described in the ECSS and ACSM consensus (Meeusen et al., 2013), is accompanied by sleep disturbances and autonomic instability; night sweats can be one of the indirect manifestations. Similar complaints are given by relative energy deficiency in sports (REDs), which affects hormonal regulation.
- Behavioral: late training, warm bedroom, alcohol, spicy food, coffee in the evening.
- Sports: overtraining, REDs, sudden changes in weight.
- Sleep: Obstructive sleep apnea, especially in large strength athletes.
- Gastrointestinal: gastroesophageal reflux.
- Infections and other diseases: tuberculosis, HIV, endocarditis, lymphomas, hyperthyroidism.
Alcohol dilates skin vessels and disrupts thermoregulation, and with regular use, evening withdrawal causes sweating and restlessness at night. Obstructive sleep apnea occurs more often in people with a large body weight and a thick neck - that is, in some weightlifters, powerlifters, and bodybuilders. Snoring, respiratory arrest and daytime sleepiness in combination with night sweats are a reason to be examined.
Finally, we must not forget about infections and oncological diseases. Night sweats along with fever and unexplained weight loss belong to the so-called "B-symptoms" of lymphoma. Although such reasons are rare in young active people, it is the doctor who excludes them in the first place if there are accompanying alarming signs.
Fat burners and stimulants
Means for a fat-loss phase is one of the most frequent pharmacological explanations for night sweats in athletes. Caffeine, synephrine, yohimbine and other stimulants increase the activity of the sympathetic nervous system and thermogenesis. If they are taken in the afternoon, sweating and superficial sleep at night are quite expected.
Clenbuterol, a β2-adrenoceptor agonist, banned by WADA and not intended for human use for weight loss, increases heat production, causes tremors, tachycardia and sweating. Thyroid hormones (triiodothyronine) create a state of artificial thyrotoxicosis; heat intolerance and sweating are classic symptoms of hyperthyroidism, described in the guidelines of the American Thyroid Association (Ross et al., 2016).
| Substance | Sweating mechanism | Level of danger |
|---|---|---|
| Caffeine, synephrine | Sympathetic stimulation, thermogenesis | Usually mild, dose dependent |
| Clenbuterol | β2-stimulation, strengthening of thermogenesis | High: arrhythmias, heart damage |
| Triiodothyronine (T3) | Iatrogenic thyrotoxicosis | High: arrhythmias, muscle wasting |
| DNP | Uncoupling of oxidative phosphorylation, uncontrolled heating | Critical: risk of death |
| Insulin (off-label) | Nocturnal hypoglycemia, release of adrenaline | Critical: risk of death |
DNP (2,4-dinitrophenol) is especially dangerous. It causes cells to "burn" energy in the form of heat, and this process is not regulated. A review by Grundlingh et al (2011) describes multiple deaths from hyperthermia; there is no antidote. Night sweats, fever, and rapid breathing against the background of DNP are signs of poisoning that require an emergency call.
Insulin, which some athletes use without medical indications, can cause nocturnal hypoglycemia. The body reacts by releasing adrenaline - hence sudden sweating, palpitations, nightmares. Severe nocturnal hypoglycemia can end in coma and death in sleep, so such a symptom cannot be ignored.
Hormones, steroids and PCT preparations
Sex hormones stabilize the work of the thermoregulation center. Therefore, when the level of testosterone or estradiol drops sharply, hot flashes and night sweats may appear. In men, this occurs with hypogonadism, in particular after the withdrawal of anabolic-androgenic steroids, when the actual production of testosterone is still suppressed (Rahnema et al., 2014).
Drugs used for so-called PCT or to control estrogens can themselves cause hot flashes. According to official guidelines, tamoxifen and aromatase inhibitors (anastrozole, letrozole) in women treated for breast cancer often cause hot flashes; clomiphene also has this side effect. The mechanism is related to the blockade of the estrogen signal in the hypothalamus. The editors do not provide schemes for their use: these drugs must be prescribed by a doctor.
Excess estrogens or their fluctuations, as well as prolactin when using some steroids can be accompanied by vegetative complaints. Growth hormone in medical use often causes fluid retention and sweating, and in excessive doses, a condition similar to acromegaly, in which increased sweating is a typical symptom.
Finally, frequent medical drugs are also important: antidepressants of the SSRI group, some antipyretics, glucocorticoids. If the night sweats coincided with the start of taking a new drug, it is worth discussing with the doctor - it may be enough to change the time of administration or the drug.
Editorial conclusion
In most athletes, night sweats have safe explanations: late training, a warm bedroom, alcohol or evening stimulants. Mode correction often solves the problem.
Pharmacological causes include fat burners, clenbuterol, thyroid hormones, sex hormone fluctuations after AAS, and drugs that affect estrogens. DNP and insulin can cause life-threatening conditions.
Night sweats along with fever, weight loss, enlarged lymph nodes, or cough require evaluation regardless of what the person is taking.
The editors recommend also reading our materials on the prevention and diagnosis of night sweats, on the dangers of DNP and on the restoration of the hormonal background after the use of steroids.
References
- Mold JW, Holtzclaw BJ, McCarthy L. Night sweats: a systematic review of the literature. J Am Board Fam Med. 2012;25(6):878â893.
- Meeusen R, Duclos M, Foster C, et al. Prevention, diagnosis, and treatment of the overtraining syndrome: joint consensus statement of the ECSS and ACSM. Med Sci Sports Exerc. 2013;45(1):186â205.
- Ross DS, Burch HB, Cooper DS, et al. 2016 American Thyroid Association guidelines for diagnosis and management of hyperthyroidism and other causes of thyrotoxicosis. Thyroid. 2016;26(10):1343â1421.
- Grundlingh J, Dargan PI, El-Zanfaly M, Wood DM. 2,4-dinitrophenol (DNP): a weight loss agent with significant acute toxicity and risk of death. J Med Toxicol. 2011;7(3):205â212.
- Rahnema CD, Lipshultz LI, Crosnoe LE, et al. Anabolic steroid-induced hypogonadism: diagnosis and treatment. Fertil Steril. 2014;101(5):1271â1279.
- Pope HG Jr, Wood RI, Rogol A, et al. Adverse health consequences of performance-enhancing drugs: an Endocrine Society scientific statement. Endocr Rev. 2014;35(3):341â375.
- World Anti-Doping Agency. The World Anti-Doping Code: International Standard — Prohibited List. Montreal: WADA; updated every year.
