Following thyroid surgery some patients develop hypocalcemia. For most this is transient, while a small group are found to have permanent hypoparathyroidism. Certain risk factors can help identify those patients at risk for permanent hypoparathyroidism. This study was done at the University of Lille in France.



(1) hypocalcemia: serum calcium < 8.0 mg/dL on at least 2 consecutive measurements.

(2) severe hypocalcemia: either (a) serum calcium < 8.0 mg/dL for more than 2 days, or (b) signs of hypocalcemia with paresthesia or positive Chvostek's sign

(3) transient hypoparathyroidism: recovery of parathyroid function within a few weeks to months after surgery

(4) permanent hypoparathyroidism: requirement for vitamin D and/or calcium supplements to maintain eucalcemia 1 year after thyroidectomy, associated with low or undetectable parathyroid hormone levels


Reference ranges for assays used in study:

(1) serum calcium: 8.1-10.4 mg/dL

(2) serum phosphorus: 2.68-4.5 mg/dL

(3) serum parathyroid hormone (PTH), intact molecule assay: 10-55 pg/mL (minimal detection 5 pg/mL)


Risk factors for permanent hypoparathyroidism:

(1) < 3 parathyroid glands preserved in situ during surgery

(2) serum PTH level <= 12 pg/mL (intact hormone assay), performed shortly after surgery (early)

(3) serum calcium <= 8 mg/dL after receiving oral calcium therapy for a week or more (delayed)

(4) serum phosphorus >= 4 mg/dL after receiving oral calcium therapy for a week or more (delayed)


number of risk factors present =

= SUM(risk factors identified)



• minimum number: 0

• maximum number: 4

• The presence of one or more factors indicates that the patient is at risk for developing permanent hypoparathyroidism.



• Patients identified as being at risk for permanent hypoparathyroidism should have long-term followup to detect hypocalcemia and to provide appropriate supplemental therapy.


To read more or access our algorithms and calculators, please log in or register.