Breathlessness on HT

 I have been on Decapeptyl now for 10 weeks.  I have been getting dizzy spells getting up from sitting or kneeling down and my GP has put it down to my body not adjusting to standing up quick enough which is something you get when you get older.  Apparently veins in the lower body are supposed to automatically adjust to get more blood pressure to the brain and upperbody when you stand up.  But what is strange is now if I walk up the stairs at it easy pace I get quite breathless and have to hold onto the doorjamb until it passes.  But I cycle regularly about 150 miles a week and once I’m out I never get any breathlessness at all.  I have read that Decapeptyl  can cause breathlessness so I suppose I better see my GP to see what he thinks it could be if anyone on here has experience of breathlessness with Decapeptyl I would be interested on the outcome