Endocrine Abstracts

JOINT3760

Background: Women who have had breast cancer treatment may have an increased risk of osteoporosis and fracture. Moreover, breast cancer might have complications like distant metastases accompanied by hypercalcemia and high alkaline phosphatase levels, but hyperparathyroidism is not commonly considered in the differential diagnosis.

Case Presentation: We present the case of a 62-year-old female, with medical history of breast cancer (2013, right breast conservatory surgery, subsequent radiotherapy and 5 years of hormonal treatment with Tamoxifen), with no tumor recurrence detectable at yearly oncology assessments, is referred to an endocrinology consult due to persistent elevated alkaline phosphatase and severe osteoporosis with lowest bone mineral density (BMD) at distal radius level (T-score of -4 SD), compared to lumbar spine (T-score L1-L4 of -2.7 SD) and hip (T-score femoral neck of -2.7 SD). Causes of secondary osteoporosis were investigated detecting elevated PTH (104 pg/ml, N:10-69), normal 25-OH-vitamin D (64.1 ng/ml, N>30, under adequate vitamin D supplementation 4000-5000IU/day), mild hypercalcemia (10.33mg/dl, N:8.5-10.3), hypercalciuria (398.4 mg/24h, N<250), normal phosphatemia (3.67 mg/dl, N:2.6-4.5). Considering vitamin D was above 40-50ng/ml, and PTH is its end-activator (by renal hydroxylation) potentially increasing hypercalcemia, we decided to stop vitamin D supplementation until investigations were completed. Cervical ultrasound identified normal thyroid gland, but a small hypochoic nodule 6.3 mm localized in the lower pole of the left thyroid lobe confirmed a parathyroid adenoma by parathyroid scintigraphy. The functional and imaging data confirmed the diagnosis of primary hyperparathyroidism, and a 3-month biological follow-up spontaneous improvement was observed: PTH of 83.32 pg/ml, 25-OH-vitamin D maintained within normal range 31.56 ng/ml, normal calcium levels (total calcium of 9.8mg/dl), normal phosphatemia.

Conclusions: We presented the case of a woman diagnosed with severe osteoporosis seven years after a breast cancer diagnosis, associating persistent elevated alkaline phosphatase levels in the absence of detectable local or distal tumor recurrence, which proved to be in the context of primary hyperparathyroidism.

Keywords: osteoporosis, breast cancer, primary hyperparathyroidism