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Clinical Crossroads | Clinician's Corner

A 64-Year-Old Woman With Primary Hyperparathyroidism

Gordon J. Strewler, MD, Discussant
JAMA. 2005;293(14):1772-1779. doi:10.1001/jama.293.14.1772.
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DR BURNS: Ms Q is a 64-year-old woman with a history of mild hypercalcemia and hyperparathyroidism. She has managed care insurance.

Ms Q states that on a routine blood test 7 years ago she was noted to have a calcium level of 10.1 mg/dL (2.5 mmol/L). She has subsequently had her calcium checked on a biannual basis and it has ranged from 10.4 to 11.3 mg/dL (2.6-2.8 mmol/L). Ms Q was referred to an endocrinologist in December 2002 after her calcium was higher than 11 mg/dL (2.7 mmol/L) on 3 occasions. Her laboratory studies just prior to her visit revealed a calcium level of 11.1 mg/dL (2.8 mmol/L), a parathyroid hormone (PTH) level of 102 pg/mL, and a phosphate level of 3.4 mg/dL.

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Figure 1. Schematic Diagram of Calcium Set Points in Healthy Individuals Compared With Individuals With Primary Hyperparathyroidism and Hypothetical Relationship to Parathyroid Adenoma Size
Graphic Jump Location

A, The normal feedback relationship between calcium and parathyroid hormone is shown. Parathyroid hormone is suppressed by calcium over the normal range for serum calcium (shaded area), with the set point for calcium at the midpoint of the curve. In all forms of hyperparathyroidism the adenoma is relatively insensitive to feedback suppression by calcium. This results in a shift to the right in the feedback relationship and an increase in the set point for serum calcium. B, An increase in the set point for serum calcium is a determinant of parathyroid adenoma growth. The adenoma size increases until it reaches a sufficient size to maintain parathyroid hormone and serum calcium at the new set point, and the adenoma then stops growing.

Figure 2.99Technicium Tc-99m–Labeled Sestamibi Scans of Thyroid and Parathyroid Glands
Graphic Jump Location

A, In the early phase, sestamibi is taken up by thyroid tissue (black arrowheads) and parathyroid (yellow arrowhead). B, Parathyroid uptake persists at a later time (yellow arrowhead).

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