Posterior pituitary function in Sheehan's syndrome.
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OBJECTIVE: We studied posterior pituitary function in 27 patients with Sheehan's syndrome and 14 controls. DESIGN: All patients were investigated by water deprivation test and 26 of them by 5% hypertonic saline infusion test. None of the patients had symptoms of diabetes insipidus and all patients were on adequate glucocorticoid and thyroid hormone replacement therapy before testing. RESULTS: According to dehydration test, 8 (29.6%) patients had partial diabetes insipidus (PDI group) and 19 (70.3%) had normal response (non-DI group). During the 5% hypertonic saline infusion test, the maximal plasma osmolality was higher in PDI (305 +/- 4.3) and non-DI (308 +/- 1.7) groups when compared with controls (298 +/- 1.7 mOsm/kg; P < 0.005), but the maximal urine osmolality was lower in PDI group (565 +/- 37) than in non-DI (708 +/- 45) and control (683 +/- 17 mOsm/kg) groups (P < 0.05). The osmotic threshold for thirst perception was higher in PDI (296 +/- 4.3) and non-DI (298 +/- 1.4) groups when compared with control group (287 +/- 1.5 mOsm/kg) (P < 0.005). Basal plasma osmolalities were also higher in PDI (294 +/- 1.0) and non-DI (297 +/- 1.1) groups than in controls (288 +/- 1.2 mOsm/kg; P < 0.001). CONCLUSIONS: Our findings demonstrated that patients with Sheehan's syndrome have an impairment of neurohypophyseal function. The thirst center may be affected by ischemic damage and the osmotic threshold for the onset of thirst in patients with Sheehan's syndrome is increased. (+info)
Differential regulation of parvocellular neuronal activity in the paraventricular nucleus of the hypothalamus following single vs. repeated episodes of water restriction-induced drinking.
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Acute activation of the hypothalamic-pituitary-adrenal (HPA) axis releases glucocorticoids to maintain homeostasis, whereas prolonged exposure to elevated glucocorticoids has deleterious effects. Due to the potential benefits of limiting stress-induced glucocorticoid secretion, the present study uses drinking in dehydrated rats as a model to delineate mechanisms mobilized to rapidly inhibit HPA activity during stress. Using Fos expression as an indicator of neuronal activation, the effect of a single or repeated episode of dehydration-induced drinking on the activity of magnocellular and parvocellular neurons in the paraventricular nucleus (PVN) of the hypothalamus was examined. Adult male rats underwent a single episode or repeated (six) episodes of water restriction and were sacrificed before or after drinking water in the AM. Plasma osmolality, vasopressin (AVP), adrenocorticotropic hormone (ACTH) and corticosterone were elevated by water restriction and reduced after drinking in both models. Fos expression was elevated in AVP-positive magnocellular PVN neurons and AVP- and corticotropin releasing hormone (CRH)-positive parvocellular PVN neurons after water restriction. Fos expression was reduced in magnocellular AVP neurons after both models of restriction-induced drinking. In contrast, Fos expression did not change in AVP and CRH parvocellular neurons after a single episode of restriction-induced drinking, but was reduced after repeated episodes of restriction-induced drinking. These data indicate that drinking-induced decreases in glucocorticoids in dehydrated rats involve multiple factors including reduction in magnocellular release of vasopressin and reduction in parvocellular neuronal activity. The differential inhibition of PVN parvocellular neurons after repeated rehydration may reflect a conditioned response to repeated stress reduction. (+info)
Sertraline, a selective serotonin reuptake inhibitor, affects thirst, salt appetite and plasma levels of oxytocin and vasopressin in rats.
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We investigated the effects of chronic administration of sertraline (SERT; approximately 20 mg kg(-1) day(-1) in drinking water), a selective serotonin reuptake inhibitor, on water and sodium intake and on plasma levels of oxytocin (OT) and vasopressin (AVP) in basal and stimulated conditions. Basal water intake was reduced in SERT-treated rats. After 24 h of water deprivation, rats treated with SERT for 21 days ingested less water than the control rats (9.7 +/- 0.5 versus 20.0 +/- 0.9 ml, respectively, at 300 min after water presentation, P < 0.0001). Subcutaneous injection of 2 m NaCl or isoproterenol evoked a lower dipsogenic response in rats treated with SERT for 21 days. Fluid and food deprivation also induced a weaker dipsogenic response in SERT-treated rats (1.6 +/- 0.5 versus 10.2 +/- 1.2 ml, at 300 min, P < 0.0001) but had no effect on saline intake. Sodium depletion induced a higher natriorexigenic response in the SERT group (5.6 +/- 1.3 versus 1.2 +/- 0.3 ml, at 300 min, P < 0.0002). Higher urinary density and lower plasma sodium levels were observed after SERT treatment. Sertraline also increased plasma levels of vasopressin and oxytocin (AVP, 2.65 +/- 0.36 versus 1.31 +/- 0.16 pg ml(-1), P < 0.005; OT, 17.16 +/- 1.06 versus 11.3 +/- 1.03 pg ml(-1), P < 0.0009, at the third week post-treatment). These data constitute the first evidence that chronic SERT treatment affects water and sodium intake in rats. These effects seem to be related to the hyponatraemia caused by the higher plasma levels of AVP and OT. (+info)
Sugars and satiety: does the type of sweetener make a difference?
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BACKGROUND: Widespread use of high-fructose corn syrup (HFCS) in beverages has been linked to rising obesity rates. One hypothesis is that HFCS in beverages has little satiating power. OBJECTIVE: The objective of the study was to compare the relative effect of commercial beverages containing sucrose or HFCS on hunger, satiety, and energy intakes at the next meal with the use of a within-subject design. DESIGN: Thirty-seven volunteers (19 men, 18 women) aged 20-29 y consumed isocaloric cola beverages (215 kcal) sweetened with sucrose, HFCS 42, or HFCS 55. HFCS 42 contains 42% fructose, and HFCS 55 contains 55% fructose. Diet cola (2 kcal), 1%-fat milk (215 kcal), and no beverage were the control conditions. The 5 beverages were consumed at 1010 (2 h after a standard breakfast). Participants rated hunger, thirst, and satiety at baseline and at 20-min intervals after ingestion. A tray lunch (1708 kcal) was served at 1230, and energy intakes were measured. The free sugars content of sucrose-sweetened cola was assayed at the time of the study. RESULTS: We found no differences between sucrose- and HFCS-sweetened colas in perceived sweetness, hunger and satiety profiles, or energy intakes at lunch. The 4 caloric beverages tended to partially suppress energy intakes at lunch, whereas the no-beverage and diet beverage conditions did not; the effect was significant (P<0.05) only for 1%-fat milk. Energy intakes in the diet cola and the no-beverage conditions did not differ significantly. CONCLUSION: There was no evidence that commercial cola beverages sweetened with either sucrose or HFCS have significantly different effects on hunger, satiety, or short-term energy intakes. (+info)
Adipsic hypernatremia in a dog with antithyroid antibodies in cerebrospinal fluid and serum.
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A 4-year-old, male Labrador retriever, weighing 27 kg, presented with abrupt clinical signs including mental retardation, circling and head pressing. The dog never ingested water by choice. An adipsia of the dog was persisted and developed to hypernatremia with artifactual hyperchloremia. Serial endocrine results and image findings were suggestive of a hypothyroidism. The dog revealed the presence of antithyroid antibodies in the cerebrospinal fluid and serum. With the administration of levothyroxine sodium, his neurologic signs were alleviated within the first week of treatment and adipsia was also resolved. (+info)
Severe rhabdomyolysis due to adipsic hypernatremia after craniopharyngioma surgery.
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The association of diabetes insipidus and adipsia after craniopharyngioma surgery has high morbidity. Hypernatremia can be caused by adipsia and be aggravated by diabetes insipidus. Rhabdomyolysis rarely occurs. CASE REPORT: This is the first report of a diabetic patient with craniopharyngioma who developed diabetes insipidus and adipsia after surgery, evolving with severe hypernatremia that caused considerable rhabdomyolysis. CONCLUSION: The importance of the evaluation of muscle integrity when under hypernatremic states is pointed out. Although adipsia may have a simple solution through volunteer water ingestion, serious consequences such as repeated severe hypernatremia episodes and intense rhabdomyolysis with high morbidity could occur, if adipsia is not diagnosed. (+info)
Effect of aging on regional cerebral blood flow responses associated with osmotic thirst and its satiation by water drinking: a PET study.
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Levels of thirst and ad libitum drinking decrease with advancing age, making older people vulnerable to dehydration. This study investigated age-related changes in brain responses to thirst and drinking in healthy men. Thirst was induced with hypertonic infusions (3.1 ml/kg 0.51M NaCl) in young (Y) and older (O) subjects. Regional cerebral blood flow (rCBF) was measured with positron emission tomography (PET). Thirst activations were identified by correlating rCBF with thirst ratings. Average rCBF was measured from regions of interest (ROI) corresponding to activation clusters in each group. The effects of drinking were examined by correlating volume of water drunk with changes in ROI rCBF from maximum thirst to postdrinking. There were increases in blood osmolality (Y, 2.8 +/- 1.8%; O, 2.2 +/- 1.4%) and thirst ratings (Y, 3.1 +/- 2.1; O, 3.7 +/- 2.8) from baseline to the end of the hypertonic infusion. Older subjects drank less water (1.9 +/- 1.6 ml/kg) than younger subjects (3.9 +/- 1.9 ml/kg). Thirst-related activation was evident in S1/M1, prefrontal cortex, anterior midcingulate cortex (aMCC), premotor cortex, and superior temporal gyrus in both groups. Postdrinking changes of rCBF in the aMCC correlated with drinking volumes in both groups. There was a greater reduction in aMCC rCBF relative to water drunk in the older group. Aging is associated with changes in satiation that militate against adequate hydration in response to hyperosmolarity, although it is unclear whether these alterations are due to changes in primary afferent inflow or higher cortical functioning. (+info)
Obestatin inhibits vasopressin secretion: evidence for a physiological action in the control of fluid homeostasis.
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