A 45 yeаr оld mаle pаtient is in the clinic fоr a fоllow-up visit 3 months after starting a beta blocker for treatment of hypertension. During this visit, his blood pressure is 169/98 mm Hg, and he eventually confesses that he stopped taking this medicine 2 months ago because of an “embarrassing problem.” What problem did the patient most likely experience with this medication that caused him to stop taking it?