Rare presentation of occult medullary carcinoma of the thyroid as a mediastinal mass.

OBJECTIVE: To describe a rare case of occult (<1 cm in diameter) medullary thyroid carcinoma (MTC) in a 45-year-old woman, presenting as an asymptomatic mediastinal mass. DESIGN: The diagnostic methodology included laboratory measurements of relevant biochemical and hormonal parameters including calcitonin (CT), carcinoembryonic antigen (CEA) and chromogranin A, and imaging techniques including ultrasound (U/S), computed tomography (C/T), magnetic resonance imaging (MRI) and radio labeled somatostatin analog ((111)In-DTPA-octreotide). RESULTS: Chest CT revealed a mediastinal mass measuring 5 cm in diameter abutting the right thyroid lobe. CEA was elevated and an association with thyroid malignancies was considered. CT was found to be markedly elevated, pointing to the diagnosis of MTC metastatic to the mediastinum. The patient underwent total thyroidectomy, lymph node dissection and removal of the mediastinal mass. Histological examination revealed MTC of the right thyroid lobe measuring 0.5 cm, metastatic to regional and superior mediastinal lymph nodes. CONCLUSIONS: Occult MTC can infrequently present as an asymptomatic mediastinal mass. Elevated serum CT and CEA along with imaging techniques leads to the correct diagnosis and surgical management of the disease.

Weightlessness and skeleton homeostasis.

As human beings venture into space in the 21st century, they will be confronted with a "hypodynamic" and thus hostile environment for the bone homeostasis, that could potentially compromise their mobility in general and skeletal strength in particular after landing. From this point of view, space flight studies are especially interesting and intriguing models for scientists. Space studies, however, must not only overcome enormous technical problems but are also limited in size and frequency. Therefore, ground-based models have also been developed to evaluate the effects of skeletal unloading. The most popular model for human studies is prolonged bed rest with normal volunteers, although studies with paraplegics have also been undertaken. In animals, the hindlimb elevation (tail suspension) model simulates space flight models and is well tolerated by the animals with minimal evidence of stress. Although negative calcium balance and bone loss have been observed in all the aforementioned models of skeletal unloading, the exact mechanism(s) by which this occurs are still unknown and mainly speculative.