Parathyroid hormone-related protein induced coupled increases in bone formation and resorption markers for 7 years in a patient with malignant islet cell tumors

Humoral hypercalcemia of malignancy in a patient with large cell carcinoma of the lung: report of case and review of literature

OBJECTIVE

To report a case of hypercalcemia associated with parathyroid hormone-related protein (PTHrP) in large cell carcinoma of the lung.

METHODS

We present a case of PTHrP-mediated hypercalcemia in a patient with a large cell carcinoma of the lung and review the related literature.

RESULTS

A 43-year-old African American man required medical attention because of lethargy, confusion, and poor oral intake. He had bullous emphysema attributable to a 50-pack-year smoking history. On physical examination, vital signs were normal, he was oriented to place and person but not time, and he had cachexia. Breath sounds were decreased in the left lower lung field. Findings on cardiac and abdominal examination were normal. Results of laboratory studies (and corresponding reference ranges) were as follows: calcium 12.1 mg/dL (8.5 to 10.5), albumin 2.0 g/dL (3.5 to 5.0), phosphorus 2 mg/dL (2.5 to 4.5), alkaline phosphatase 68 U/L (40 to 150), intact parathyroid hormone 5 pg/mL (10 to 60), PTHrP 7.0 pmol/L (0.0 to 1.5), 1,25-dihydroxyvitamin D 20.8 pg/mL (25.1 to 66.1), and 25-hydroxyvitamin D 3.7 ng/mL (10 to 60). Computed tomographic scans of the chest showed a large complex lesion in the left lower hemithorax, a small right pleural effusion, and extensive pulmonary emphysema bilaterally. Open lung biopsy revealed a large cell undifferentiated carcinoma. Abdominal and pelvic computed tomographic scans showed no evidence of metastatic involvement. A bone scan was negative for osseous metastatic lesions.

CONCLUSION

Although the finding is rare, patients with large cell carcinoma of the lung and hypercalcemia may have humoral hypercalcemia mediated by PTHrP.

Métabolisme minéral osseux: données récentes et perspectives relatives à l’ostéogenèse

Important data have recently been added to our knowledge of bone mineral metabolism in children. Molecular pathophysiology of several pediatric syndromes has been clarified. Specially, the components of endocrine and metabolic regulations are tightly related with regard to the trophicity of bone. On another hand, the impact of several therapeutics of bone diseases like biphosphonates, parathormone (PTH) or growth hormone on bone anabolism is now strongly emphasized. All these points are important for the becoming of bone pediatric diseases in the adult life. Here we analyze the essential components of mineral metabolism and of its regulation in view of the recent biological data, like PTH/PTHrP (PTH-related peptide)-evoked cell signaling, the role of FGF 23 (Fibroblast growth factor 23) in hypophosphatemia and the regulation of vitamin D metabolism by 1alpha-hydroxylase. Inter-relation of these regulating elements is present in several genetic diseases and in the Mc Cune Albright syndrome. Relationships between metabolic and endocrine factors are analyzed considering their impact on PTH secretion and osteogenesis.

Osteoporosis in HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP)

Human T-cell lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) has been associated with changes in extracellular matrix of neural tissue. HTLV-I infection has multiple other systemic effects. Extracellular matrix is important for bone mineral deposition. We examined bone mineral density (BMD) in patients with HAM/TSP. BMD was assessed by ultrasonographic calcaneous densitometry in 24 patients (7 males, 17 females) with HAM/TPS, and 23 healthy HTLV-I-seronegative controls matched by age and sex. Patients with HAM/TPS had a mean BMD T-score of -3.07 +/- 0.64 in males and -2.93 +/- 0.69 in females. Control patients revealed a T-score of -0.77 +/- 1.31 in males and -1.17 +/- 1.08 females. The difference in T-score between HAM/TSP patients and control groups is significant (P < 0.001). Of HAM/TPS patients, 7 of 24 (29.2%) had osteopenia (T-score between -1 and -2.5) and 17 of 24 (70.8%) were diagnosed with osteoporosis (T < -2.5). Respective figures for control patients were 10 of 23 (43.5%) with a normal T-score, 11 of 23 (47.8%) with osteopenia, and 2 of 23 (8.7%) with osteoporosis. After adjustment for age and sex, odds ratio of osteoporosis for HAM/TSP patients was 31.52 (95% confidence interval, 5.07 to 195.88). No correlation was found in HAM/TSP patients between T-score and age, menstrual status, gait functionality, or years of evolution of HAM/TSP. HAM/TSP patients have a significantly diminished BMD of the calcaneous that appears not to be explained by paresis, age, years of disease, menstrual status; may be the result of systemic alterations due to HTLV-1 infection.

Hyperparathyroidism, humoral hypercalcemia of malignancy, and the anabolic actions of parathyroid hormone and parathyroid hormone-related protein on the skeleton

So what have we learned from the Takeuchi case? It has been 80 years since malignancy-associated hypercalcemia was described. It has been 45 years since HHM was first described. It has been 15 years since PTHrP was identified, and 12 years since PTHrP immunoassays became available for clinical research. We now know almost everything about HHM in pathophysiological terms, and we can reproduce the cardinal features of the syndrome in laboratory animals and humans. The Takeuchi case reminds us that we still have a few things to learn about HHM. Specifically, "Why is the regulation of 1,25(OH)2D different in patients with HHM and HPT?" and "Why is normal osteoblast-osteoclast coupling dysregulated in HHM?" or more fundamentally, "What regulates osteoblast-osteoclast coupling, and why is it deranged in HHM?" Given the rate of accumulation of new information about HHM, about the anabolic effects of PTH and PTHrP, and about osteoblast-osteoclast coupling over the past 10 years, there is reason to be optimistic that the answers to these questions will soon become clear.