Finasteride has been known to cause hypogonadism in some men and this often results in gynecomastia.
http://www.propeciasideeffects.com/ Below is what Eugene Shippen, one of the worlds leading experts on hypogonadism has to say about propecia and Proscar.
Finisteride (propecia-Proscar)
From: Eugene Shippen, M. D.
Date: 5/15/01
Time: 3:42:23 PM
Remote Name: 152.163.195.186
Comments
I have become aware of a growing number of young men who started to take propecia for male pattern baldness. After relatively short intervals these men develop full symptoms of hypogonadism: decreased libido, sexual dysfunction, ED, fatigue, gynecomastia and depression. Testing shows low T and DHT, high E2, low or normal FSH/LH and normal prolactin. What is really troubling is the lack of response to T replacement, clomiphene stimulation, HCG injections. There may be significant increase in T after various methods of increasing it, but the response in all areas seems to be lacking entirely! If anyone has patients with these complaints after finisteride, please let me know as I am collecting case histories of this serious, though uncommon problem. Also, anyone who has had success with treatment, let me know at: ershippen@aol.com.
You need to find out if there is a problem with your hormones as a result of finasteride as opposed to trying to self medicate with Tamoxifen.
Tamoxifen can cause problems with thyroid function if estradiol's effects are lowered too much; an indication of this is sometimes a sore throat.
Again another indication that you need to have your hormonal health looked at by an expert.
Tamoxifen lowers estrogen's effects, but it is not very unlikely to be an adequate answer to your problem if it is not due to excess estrogen but a lowered androgen status.
You need to see an endocrinologist and you need to get at least the following tested.
LH
Serum Testosterone + SHBG or Free Testosterone
Estradiol
Prolactin
TSH, Free T4 and T3
Dihydrotestosterone
If you let me know where you live I will try and get you the contact details of good endocrinologists in your area that might be able to help.
Modified- just seen the post from aux having just posted- he is spot on.