What is the best course of action for a patient with a low Thyroid-Stimulating Hormone (TSH) level, normal Thyroxine (T4) level, and hypercalcemia, with a history of thyroid nodules and similar lab results from a previous test?

Immediate Workup for Concurrent Hyperthyroidism and Hypercalcemia

You need urgent evaluation for primary hyperparathyroidism, as the combination of suppressed TSH (0.01), normal T4 (1.6), elevated calcium (12.4), and thyroid nodules strongly suggests coexisting autonomous thyroid function and parathyroid disease—not hypercalcemia from thyrotoxicosis alone. 1, 2

Critical Diagnostic Steps

Confirm the Hyperthyroidism Source

• Obtain thyroid scintigraphy immediately to determine if your nodules are "hot" (autonomously functioning) 1, 3
• Hot nodules with suppressed TSH indicate toxic adenoma or toxic multinodular goiter 3, 4
• This is essential because hypercalcemia that persists despite treating hyperthyroidism indicates a separate parathyroid problem 1, 2

Evaluate for Primary Hyperparathyroidism

• Measure intact parathyroid hormone (PTH) now 1, 2
• If PTH is elevated or inappropriately normal with calcium of 12.4 mg/dL, this confirms primary hyperparathyroidism 1
• The combination of hot thyroid nodules and hyperparathyroidism occurs more frequently than expected by chance alone, particularly in iodine-deficient areas 1

Distinguish True Coexistence from Thyrotoxic Hypercalcemia

• Hyperthyroidism alone can cause mild hypercalcemia (typically <11 mg/dL) that resolves with treatment 1, 2
• Your calcium of 12.4 mg/dL is too high to attribute solely to thyrotoxicosis 1, 2
• If hypercalcemia persists after achieving euthyroidism, parathyroid disease is confirmed 1

Recommended Imaging Sequence

Thyroid Assessment

• Thyroid ultrasound has already identified nodules 3, 4
• Proceed with 99mTc-pertechnetate thyroid scintigraphy to characterize nodule function 1, 3, 2
• Hot nodules are rarely malignant and do not require fine-needle aspiration 3, 4

Parathyroid Localization (if PTH elevated)

• Dual-phase 99mTc-sestamibi scintigraphy with SPECT/CT to localize parathyroid adenoma 2
• Be aware that sestamibi can occasionally show uptake in thyroid nodules, potentially mimicking intra-thyroidal parathyroid adenoma 2
• Correlation with thyroid scintigraphy prevents misdiagnosis 2

Treatment Algorithm

If Both Conditions Confirmed

Combined surgical approach is recommended: 1

• Subtotal thyroidectomy for toxic nodules
• Parathyroid adenoma resection during same operation
• This prevents two separate surgeries and addresses both causes of your symptoms 1

Expected Postoperative Course

• Calcium and PTH levels normalize after parathyroid resection 1
• TSH levels increase after thyroid resection (previously suppressed by autonomous function) 1
• Both hypercalcemia and hyperthyroidism resolve simultaneously 1

If Only Hyperthyroidism Confirmed

• Radioactive iodine ablation for toxic adenoma 2
• Monitor calcium levels after achieving euthyroidism 1, 2
• If hypercalcemia persists, reassess for hyperparathyroidism 1

Critical Pitfalls to Avoid

• Never assume hypercalcemia is solely from hyperthyroidism when calcium exceeds 11 mg/dL 1, 2
• Do not delay PTH measurement—this is the key diagnostic test 1
• Avoid treating hyperthyroidism alone without evaluating parathyroid function when significant hypercalcemia is present 1
• Do not rely on ultrasound alone—scintigraphy is essential to characterize nodule function and localize parathyroid pathology 1, 3, 2
• Recognize that normal TSH does not exclude compensated hot nodules that may become overtly toxic 1

Monitoring Strategy

• Recheck calcium levels 2-4 weeks after initiating hyperthyroidism treatment 1, 2
• Persistent hypercalcemia mandates parathyroid evaluation regardless of thyroid status 1
• If surgery is performed, verify normalization of both calcium and TSH postoperatively 1