I took a xanax (alprazolam) the day before my hormone test and the testcame back normal, besides high prolactin. could xanax (alprazolam) be the cause of this?

No: No. Prolactin is controlled by Dopamine and xanax (alprazolam) has no effect. On Dopamine receptors.

Rare, but possible: There are some cases of xanax (alprazolam) causing elevated prolactin & galactorrhea. http://www.ncbi.nlm.nih.gov/pubmed/21448116 also there are research reports of elevated prolactin following xanax (alprazolam) dosing: http://www.Ncbi.Nlm.Nih.Gov/pubmed/2098668 the latter study used a dose of 3mg, and the patient in the first paper was on 5-6 mg xanax (alprazolam). These are all high doses, and you didn't say how much you took.