Complete removal of a parathyroid adenoma can be documented during surgery by demonstrating an appropriate fall in the serum parathyroid hormone (PTH) concentration.
(1) Measurement of serum parathyroid hormone concentration prior to surgery (if more than has been done use the highest value).
(2) Measurement of the serum parathyroid hormone concentration 10-15 minutes after removal of the suspected adenoma.
The accepted criterion for complete removal of the parathyroid adenoma is a > 50% decline in the serum PTH ("Miami criterion").
decline in serum PTH =
= ((baseline PTH) - (PTH at 10 minutes after)) / (baseline PTH) * 100%
Chiu et al combined the decline in PTH with the serum PTH concentration after adenoma removal being within the normal reference range.
If the serum parathyroid hormone level does not fall as expected:
(1) Redraw a new blood sample and repeat the PTH level to see if it has fallen sufficiently.
(2) Perform a frozen section on the removed tissue to confirm that it is parathyroid tissue.
(3) Explore the patient on the ipsilateral side for additional parathyroid tissue. If a second lesion is found repeat the serum PTH monitoring to document a decline.
(4) If all else fails perform a complete bilateral neck dissection.
(1) The PTH assay must be rapid, accurate and precise to be of value.
(2) Biegelmayer et al found that in patients with hyperparathyroidism secondary to renal failure the assay for biologically active PTH (1-84) was more reliable than an assay for the intact hormone.
(3) The equipment and assay for PTH measurement is expensive. Stalberg et al feel that preoperative localization studies may be more cost-effective. However, Carneiro-Pla et al felt that felt that it significantly improved the success of surgery, especially if multiple adenomas are present.
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Specialty: Endocrinology, Clinical Laboratory, Orthopedic Surgery