Human adrenal glands secrete vitamin C in response to adrenocorticotrophic hormone.

BACKGROUND: When vitamin C intake is from foods, fasting plasma concentrations do not exceed 80 micromol/L. We postulated that such tight control permits a paracrine function of vitamin C. OBJECTIVE: The purpose of this study was to determine whether paracrine secretion of vitamin C from the adrenal glands occurs. DESIGN: During diagnostic evaluation of 26 patients with hyperaldosteronism, we administered adrenocorticotrophic hormone intravenously and measured vitamin C and cortisol in adrenal and peripheral veins. RESULTS: Adrenal vein vitamin C concentrations increased in all cases and reached a peak of 176 +/- 71 micromol/L at 1-4 min, whereas the corresponding peripheral vein vitamin C concentrations were 35 +/- 15 micromol/L (P<0.0001). Mean adrenal vein vitamin C increased from 39 +/- 15 micromol/L at 0 min, rose to 162 +/- 101 micromol/L at 2 min, and returned to 55 +/- 16 micromol/L at 15 min. Adrenal vein vitamin C release preceded the release of adrenal vein cortisol, which increased from 1923 +/- 2806 nmol/L at 0 min to 27 191 +/- 16 161 nmol/L at 15 min (P<0.0001). Peripheral plasma cortisol increased from 250 +/- 119 nmol/L at 0 min to 506 +/- 189 nmol/L at 15 min (P<0.0001). CONCLUSIONS: Adrenocorticotrophic hormone stimulation increases adrenal vein but not peripheral vein vitamin C concentrations. These data are the first in humans showing that hormone-regulated vitamin secretion occurs and that adrenal vitamin C paracrine secretion is part of the stress response. Tight control of peripheral vitamin C concentration is permissive of higher local concentrations that may have paracrine functions.

MR imaging features of thyrotropin-secreting pituitary adenomas at initial presentation.

OBJECTIVE: We report the MR imaging characteristics of thyrotropin-producing pituitary adenomas at their initial presentation and also report the role of MR imaging in predicting surgical outcome in these rare tumors. MATERIALS AND METHODS: We reviewed the records and MR images of 21 patients with thyrotropin-producing pituitary adenomas from 1984 to 1999. The imaging features of these tumors were examined, including enhancing characteristics and tumor volumes. A staging system of tumor invasion was designed by grading cavernous and sphenoid sinus invasion and suprasellar extension. A cumulative invasion score was then used as a predictor of short-term surgical outcome. RESULTS: Twenty patients had macroadenomas, and one patient had a microadenoma. In 17 of 21 patients, the thyrotropin-producing pituitary adenoma was clearly visualized as a hypoenhancing mass compressing the normal pituitary gland. Conversely, in four patients, the pituitary gland was not discernible because of complete distortion by the adenoma. Thyrotropin-producing pituitary adenomas were large and showed a tendency to invade surrounding structures. Tumor volume ranged from 0.42 to 94.2 cm(3) (mean +/- SD, 16.0 +/- 17.8 cm(3)). The mean score of tumor invasion was 4.77 +/- 2.06 of a maximal possible value of 9.0. A high staging score was found to be predictive of an unfavorable response to surgery. CONCLUSION: Thyrotropin-producing pituitary adenomas are usually large tumors at initial presentation with hypoenhancing features compared with normal pituitary tissue; they tend to be invasive. Greater amounts of invasion correlate with incomplete surgical removal of the tumor and continued hormonal secretion.

Persistent primary hyperparathyroidism caused by adenomas identified in pharyngeal or adjacent structures.

Abnormalities in the normal migration of the parathyroid glands during embryological development of the head and neck may result in considerable variability in the location of parathyroid tissue. Ectopic parathyroid adenomas present diagnostic and technical challenges and are frequently the cause of persistent primary hyperparathyroidism (HPT) after unsuccessful initial parathyroid surgery. We report a series of eight patients with persistent primary HPT who had adenomas in rare and unusual locations associated with various pharyngeal structures. Four were located within the epineurium of the vagus nerve at or above the level of the carotid bifurcation, and four were located within the paranasopharyngeal space or oropharynx. Noninvasive and invasive preoperative imaging studies were crucial in localizing the neoplasms in these patients and permitted the use of a direct surgical approach, resulting in cure in all patients and a low complication rate. The location of parathyroid glands in high pharyngeal and cervical structures is a consequence of anomalous or arrested descent through developing pharyngeal structures and illustrates the remarkable spectrum of ectopic parathyroid adenomas that occur secondary to this phenomenon.

Successful management of spinal dural arteriovenous fistulas undetected by arteriography. Report of three cases.

Spinal dural arteriovenous fistulas (AVFs) frequently cause progressive myelopathy. When they are localized by imaging studies, surgery can be safely performed by simply interrupting the vein draining the fistula intradurally, and the results will be excellent and lasting. In some patients with clinical features of a spinal dural AVF and in whom magnetic resonance imaging and/or myelography findings are consistent with a diagnosis of a spinal dural AVF, however, spinal arteriography demonstrates no such results. The authors used a simple strategy based on knowledge of the epidemiology, pathophysiology, and anatomy of spinal dural AVFs to manage these cases successfully. In two patients, atherosclerotic occlusion was the primary cause for the failure of arteriography to visualize the dural AVF. The presence of an aortic aneurysm was an additional contributing factor preventing arteriographic visualization in one of these patients. In a third patient, massive obesity, and aortic atheroslerosis and tortuosity contributed to the absence of findings on three spinal arteriograms before surgical exploration lead to a more focused arteriographic examination that was successful.