Drinking enough to cause a hangover has been found to lower testosterone levels for 12 to 20 hours later- in one study to 20 percent that of their levels before drinking.
Estradiol the most potent estrogen also increases quite dramatically after drinking significant amounts. I have seen guys whose typical estradiol levels were around 130pmol/l who have had levels of over 230pmol/l post binge drinking.
That said the above are only short term effects that do not have a significant impact on the endcrine system.
But what of long term heavy drinking or binge drinking?
Malcolm Carruthers (world leading endocrinologist) said that 30% of his first 1000 patients who presented with hypogonadism in middle age reported drinking more than 21 UK units of alcohol a week.
So we know that long term heavy or binge drinking can cause hypogonadism and we also know that hypogonadism and gynecomastia are associasted conditions with 10 percent of all gynecomastia sufferers thought to be hypogonadal.
Quoting Malcolm Carruthers from his book The Testosterone Revolution.
A sixteenth centuary Italian Physician called Cornaro wrote, The excesses of youth are like drafts upon our age, payable with interest about twenty years after date". This is certainly true when it comes to alcohol. As well as those 30 percent of patients who were drinking too much, anout another 10 percent gave a past history of excess alcohol consumption for over a year or more. Unfortunately, testicular function does not seem to improve very much even if they subsequently stop drinking for several years.
This is in contrast to smoking, where most of the hazards, such as lung cancer and heart disease, decrease dramatically within five to ten years of giving up. The testis lacks the power of the liver to regenerate and never fully recovers, as is shown by the infertility, impotence and loss of libido that chronic alcoholics experience, even after drying out. The liver forgives and forgets, but the testis harbors grudges, so bar room bruisers of today are likely the lousy lovers of tomorrow.
Unquote
So light social drinking is ok in the long term, moderate drinking a potential hazard in the long term and heavy or binge drinking in the long term a real concern and distinct possible indirect cause for developing gynecomastia.
A good job my testosterone comes out of a packet is all I can say- I drink infrequently, but too excess