Can a copper deficiency cause hair loss?

You'll want to see a physician if concerned. Copper deficiency is rare because we as humans need so little copper. There are a number of causes of copper deficiency including genetic syndromes, gastrointestinal issues, celiac disease, excessive zinc intake and others.  If there are no other physical or biochemical manifestations of copper deficiency (ie anemias, neurological issues, etc) it would be unusual for supplementation to trigger growth. However, exceptions exist so be sure to see a physician to discuss causes and necessity of treatments.

This is highly unusual. In my entire career I don't believe that I have heard of a connection between low copper and hair loss; however a quick look through google shows that a low copper level can cause hair loss