A week of intensive sauna: what it did to hormone levels
Seven days of twice-daily sauna produced large but short-lived hormone changes in a tiny study, with an extreme protocol nobody uses day to day.
The short version
In this small 1986 study, 10 men and 7 women did an intensive protocol: one hour in an 80°C sauna, twice a day, for seven days, about two hours of sauna daily. In the men, growth hormone rose sharply within days, prolactin also rose, and cortisol and ACTH were slightly lower by the end of the week. Testosterone, thyroid hormones, FSH and LH did not change. Most of the female participants had a temporary disruption to their menstrual cycle afterward. This was an extreme, unsupervised protocol in a tiny sample, not a description of ordinary sauna bathing.
Keep in mind
This was an extreme, unsupervised protocol, 2 hours of 80°C sauna a day for a week, in 10 men and 7 women, with no control group. Most female participants had a temporary disruption to their menstrual cycle.
What they found
In the men, growth hormone rose about 16-fold by the third day of the protocol, then declined. Prolactin rose about 2.3-fold in men and more than 4-fold in the women who were measured.
Cortisol and ACTH were slightly lower by the end of the week. Testosterone, FSH, LH and thyroid hormones showed no significant change, and urinary catecholamines rose only slightly.
Most of the female participants, five of the seven, had a temporary disruption to their menstrual cycle after the week of intensive sauna use.
What this means for your practice
This does not establish a sauna routine to follow, let alone one that raises hormones. A typical sauna session bears little resemblance to two hours of 80°C heat exposure repeated daily for a week.
It is not evidence that sauna raises testosterone; this study found no change in it at all.
Methods and limitations
What the researchers did
Ten men and seven women underwent an intensive sauna protocol: one hour in an 80°C sauna, twice a day, for seven consecutive days, about 14 hours of sauna exposure in total. Blood and urine were sampled throughout the week.
This was an intervention study with no control group and no comparison to normal sauna habits; every participant did the same intensive protocol.
Growth hormone, prolactin, cortisol, ACTH, testosterone, FSH, LH, thyroid hormones and urinary catecholamines were all measured. Women were only included in the prolactin measurements, not the full hormone panel.
This is one of the most-cited sources for claims that sauna dramatically raises growth hormone, so it’s worth seeing exactly what it did and didn’t test.
How much can this tell us?
With 17 people and no control group, this study can show that an extreme heat protocol changes some hormones sharply and briefly. It cannot tell us what happens with ordinary, moderate sauna use, which this protocol does not resemble.
The 16-fold growth hormone figure often circulates on its own. In context, it followed roughly 14 cumulative hours of sauna in a week, a protocol nobody uses day to day, and the increase had already started falling by day 3.
The menstrual disruption in most of the female participants is a reminder that an intensive, unsupervised heat protocol like this one is not without effects on the body, even though it was short-lived in this small study.
What makes it useful
- One of the more detailed hormone panels measured across a full week of sauna use
- Included both men and women, even though not in the same measurements
- Directly tested an extreme protocol, rather than assuming effects from short exposures
What limits it
- Very small: 10 men and 7 women, with women measured only for prolactin
- No control group
- An extreme protocol, about 2 hours of 80°C sauna daily for a week, that does not reflect ordinary sauna use
- Most female participants had a temporary disruption to their menstrual cycle afterward
Where this study fits
Where this study fits
We score claims, not single studies. This one is part of the evidence for:
Sauna raises growth hormone. Early signal
Very low certaintyLarge effectBody signals
Sauna and cold water raise testosterone. Not supported
Low certaintyNo effect foundBody signals
Read the original
Leppäluoto J, Huttunen P, Hirvonen J, et al. Endocrine effects of repeated sauna bathing. Acta Physiol Scand. 1986;128(3):467-470.
DOI 10.1111/j.1748-1716.1986.tb08000.x · PubMed 3788622