A few weeks later 

Mr. Mason has finished his H. pylori eradication regimen but continues to take the PPI to allow for ulcer healing.  

On Sunday morning, the Masons are getting ready to go to church. It is a cold, winter morning and it has been snowing for the best part of the night. Mr. Mason is walking to his car, when he slips on a patch of ice and falls on the staircase. In addition to his bruised ego, Mr. Mason is in a lot of pain and is clutching his arm. 

Mrs. Mason takes him to the hospital, where a humerus fracture is diagnosed. 

An adverse effect due to which drug could have contributed to Mr. Mason's fracture risk?