It’s not a high serum DHT that contributes to hair loss–no! It is an elevated 5-alpha reductase level. In fact just to be clear, research shows that a high blood level of DHT is inversely correlated to balding. However, a high 5-alpha reductase level can increase DHT in local tissues, and that appears to be the factor in hair loss. Getting that important discussion out of the way, there are many hidden reasons why the enzyme 5-alpha reductase increases. Sometimes it is a result of medication, other times it could be thyroid problem and/or an endocrine system problem.
The prescription drug Reglan (metoclopramide), often used to treat gastric esophageal reflux disease (GERD), nausea, vomiting, and heartburn can cause a problem with 5-alpha reductase enzyme. The side effect of this drug can be hair loss.  Upon administration of the drug Reglan in adult rats, both 5-alpha reductase isozymes (I & II) in prostate induced prolactin secretion. Reglan induced a condition called hyperprolactinemia (elevated prolactin levels), which modifies prostate disease in animals with reduced serum plasma testosterone levels.
Elevation of prolactin also causes hair loss in males
The bottom line is, avoid any drug that raises prolactin levels if you’re interested in keeping your hair. If you’re taking this drug, consider natural alternatives. In most cases, food allergies, thickened bile, intestinal dysbiosis, or insufficient stomach acid could be the reason for digestive issues.
Effects of metoclopramide on mRNA levels of steroid 5α-reductase isozymes in prostate of adult rats.