Hyperparathyroidism: Primary, Secondary, Tertiary

Primary: Elevated PTH that results in elevated Ca2+. Typically caused by parathyroid adenoma. 

Secondary: Elevated PTH due to Low Ca2+ (Hypocalcemia). Seen commonly in chronic kidney disease causing low Vitamin D synthesis and hyperphosphatemia. Also seen in several malabsorptive states (i.e chronic pancreatitis).

Tertiary: Elevated PTH due to hyperplasia/ hypersecretion from the paraythroid gland in the setting of long-standing secondary hyperparathyroidism (i.e CKD). This results in elevated PTH AND elevated Ca2+, even after correction of the secondary cause. 

REFERENCES

1. Pitt SC, Sippel RS, Chen H. Secondary and Tertiary Hyperparathyroidism, State of the Art Surgical Management. The Surgical clinics of North America. 2009;89(5):1227-1239. doi:10.1016/j.suc.2009.06.011.
2. Ahmad R., Hammond JM. Primary, secondary, and tertiary hyperparathyroidism. Otolaryngol Clin North Am. 2004 Aug;37(4):701-13, vii-viii.
3. Russell RI. Hypoparathyroidism and malabsorption. British Medical Journal. 1967;3(5568):781-782.