Hello.. Most common cause of high PTH is secondary to vit D deficiency..Other important cause is primary hyperpathyroidism, this condition if present require complete workup with scans and further management...!!
U need to total Ca, Po4, ALPo4, serum
albumin, Vit D, serum creat along with urinary ca and urine creat level.. Consult endocrinologist.. U can do online nowadays
Next Steps
Get above Blood investigations..!!