B-HCG and LH,FSH,TSH share same alpha subunit, so HCG can activate those receptors if its in high enough quantity. Activating LH receptor will lead to more Testosterone from the Leydig cells. More testosterone can lead to more estrogen formation via aromatase.
Testicles have significant aromatase activity. This enzymatic activity is regulated by LH (and of course bHCG)