Biomedical subjects

Nicholas Frank

Publications and source records attributed to Nicholas Frank.

16 recordsLinked to original sources

PubMed2006

Physical characteristics, blood hormone concentrations, and plasma lipid concentrations in obese horses with insulin resistance.

OBJECTIVE: To compare obese horses with insulin resistance (IR) with nonobese horses and determine whether blood resting glucose, insulin, leptin, and lipid concentrations differed between groups and were correlated with combined glucose-insulin test (CGIT) results. ANIMALS: 7 obese adult horses with IR (OB-IR group) and 5 nonobese mares. PROCEDURES: Physical measurements were taken, and blood samples were collected after horses had acclimated to the hospital for 3 days. Response to insulin was assessed by use of the CGIT, and maintenance of plasma glucose concentrations greater than the preinjection value for > or = 45 minutes was used to define IR. Area under the curve values for glucose (AUC(g)) and insulin (AUC(i)) concentrations were calculated. RESULTS: Morgan, Paso Fino, Quarter Horse, and Tennessee Walking Horse breeds were represented in the OB-IR group. Mean neck circumference and BCS differed significantly between groups and were positively correlated with AUC values. Resting insulin and leptin concentrations were 6 and 14 times as high, respectively, in the OB-IR group, compared with the nonobese group, and were significantly correlated with AUC(g) and AUC(i). Plasma nonesterified fatty acid, very low-density lipoprotein, and high-density lipoprotein-cholesterol (HDL-C) concentrations were significantly higher (86%, 104%, and 29%, respectively) in OB-IR horses, and HDL-C concentrations were positively correlated with AUC values. CONCLUSIONS AND CLINICAL RELEVANCE: Measurements of neck circumference and resting insulin and leptin concentrations can be used to screen obese horses for IR. Dyslipidemia is associated with IR in obese horses.

Animals↗

PubMed2006

Blood lipid concentrations and lipoprotein patterns in captive and wild American black bears (Ursus americanus).

OBJECTIVE: To compare blood lipid concentrations and lipoprotein patterns for captive and wild American black bears (Ursus americanus). ANIMALS: 7 captive and 9 wild adult (> or = 4 years old) black bears. PROCEDURE: Blood was collected from 2 groups of captive black bears (groups A and B) and 1 group of wild black bears (group C). Blood triglyceride (TG) and cholesterol concentrations were compared among groups. Plasma lipoproteins were isolated by use of a self-generating gradient of iodixanol, and lipoprotein patterns were compared between groups A and B. RESULTS: Captive bears (mean +/- SD, 187.8 +/- 44.4 kg) weighed significantly more than wild bears (mean, 104.8 +/- 41.4 kg), but mean body weight did not differ between groups A and B. Mean blood TG concentrations for groups B (216.8 +/- 16.0 mg/dL) and C (190.7 +/- 34.0 mg/dL) were significantly higher than that of group A (103.9 +/- 25.3 mg/dL). Mean blood cholesterol concentration was also significantly higher for group B (227.8 +/- 8.2 mg/dL) than for groups A (171.7 +/- 35.5 mg/dL) or C (190.8 +/- 26.8 mg/dL). Mean very-low-density lipoprotein TG and low-density lipoprotein cholesterol concentrations were 2- and 3-fold higher, respectively, for group B, compared with concentrations for group A. CONCLUSIONS AND CLINICAL RELEVANCE: Blood lipid concentrations vary significantly among populations of black bears. Plasma lipoprotein patterns of captive bears differed significantly between colonies and may have reflected differences in diet or management practices.

Animals↗

PubMed2006

Effects of dexamethasone and isoflupredone acetate on plasma potassium concentrations and other biochemical measurements in dairy cows in early lactation.

OBJECTIVE: To determine whether administration of isoflupredone acetate (ISO) to healthy cows increases the frequency of severe hypokalemia and whether dexamethasone (DEX) has detectable mineralocorticoid properties. ANIMALS: 33 cows at 20 to 25 days of lactation. PROCEDURES: Cows were randomly allocated to 5 treatment groups and received 2 IM injections (on days 0 and 2) of sterile saline (0.9% NaCl) solution (10 mL each), an injection of ISO (20 mg) or DEX (20 mg) followed by 10 mL of saline solution, or 2 injections of ISO or DEX. Milk production was measured, physical examinations were performed, and blood and urine samples were collected daily on days 0 through 7. RESULTS: Physical examination parameters did not differ among groups; however, 1 cow developed atrial fibrillation on day 4. Both corticosteroids significantly increased plasma glucose concentrations, and ISO significantly decreased plasma potassium concentrations and increased total carbon dioxide concentrations with time. One dose of ISO decreased mean plasma potassium concentration by 25% on day 2, compared with day 0, and severe hypokalemia (serum potassium concentration < 2.3 mEq/L) developed in 1 of 6 cows. Mean plasma potassium concentration was 46% lower on day 3 than on day 0 in cows receiving 2 doses of ISO, and 5 of 7 cows became severely hypokalemic. Mean urinary fractional excretion of potassium significantly increased from that on day 0 in cows receiving 2 doses of ISO. CONCLUSIONS AND CLINICAL RELEVANCE: Both corticosteroids had glucocorticoid activity; however, only ISO had mineralocorticoid activity. Compared with saline solution, administration of 2 doses of ISO significantly increased the frequency of severe hypokalemia.

Animals↗

PubMed2005

Effects of oral administration of levothyroxine sodium on serum concentrations of thyroid gland hormones and responses to injections of thyrotropin-releasing hormone in healthy adult mares.

OBJECTIVE: To determine the effects of levothyroxine sodium (L-T4) on serum concentrations of thyroid gland hormones and responses to injections of thyrotropin-releasing hormone (TRH) in euthyroid horses. ANIMALS: 12 healthy adult mares. PROCEDURE: 8 horses received an incrementally increasing dosage of L-T4 (24, 48, 72, or 96 mg of L-T4/d) for weeks 1 to 8. Each dose was provided for 2 weeks. Four additional horses remained untreated. Serum concentrations of total triiodothyronine (tT3), total thyroxine (tT4), free T3 (fT3), free T4 (fT4), and thyroid-stimulating hormone (TSH) were measured in samples obtained at weeks 0, 2, 4, 6, and 8; 1.2 mg of TRH was then administered i.v., and serum concentrations of thyroid gland hormones were measured 2 and 4 hours after injection. Serum reverseT3 (rT3) concentration was also measured in the samples collected at weeks 0 and 8. RESULTS: Treated horses lost a significant amount of weight (median, 19 kg). Significant treatment-by-time effects were detected for serum tT3, tT4, fT3, fT4, and TSH concentrations, and serum tT4 concentrations were positively correlated (r, 0.95) with time (and therefore dosage) in treated horses. Mean +/- SD serum rT3 concentration significantly increased in treated horses (3.06 +/- 0.51 nmol/L for week 8 vs 0.74 +/- 0.22 nmol/L for week 0). Serum tT3, tT4, fT3, and TSH concentrations in response to TRH injections differed significantly between treated and untreated horses. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of levothyroxine sodium increased serum tT4 concentrations and blunted responses toTRH injection in healthy euthyroid horses.

Analysis of Variance↗

PubMed2005

Effects of oral administration of levothyroxine sodium on concentrations of plasma lipids, concentration and composition of very-low-density lipoproteins, and glucose dynamics in healthy adult mares.

OBJECTIVE: To evaluate glucose and lipid metabolism in healthy adult horses administered levothyroxine sodium (L-T4). ANIMALS: 12 healthy adult mares. PROCEDURE: 8 horses received an incrementally increasing dosage of L-T4 (24, 48, 72, or 96 mg of L-T4/d) for weeks 1 to 8. Each dose was provide between 7 AM and 8 AM in the morning grain meal for 2 weeks. Four additional horses remained untreated. Serum concentrations of nonesterified fatty acids, triglyceride (TG), total cholesterol (TC), and very-low-density lipoprotein (VLDL) were measured and composition of VLDL examined in samples obtained between 8 AM and 9 AM at weeks 0, 2, 4, 6, and 8. Glucose dynamics were assessed by use of a combined IV glucose-insulin tolerance test (IVGITT) conducted before and at the end of the 8-week treatment period. Data for each combined IVGITT were interpreted by use of the minimal model. RESULTS: Plasma TG, TC, and VLDL concentrations significantly decreased over time in treated horses. At the completion of the 8-week treatment period, mean plasma VLDL concentration was 46% of the mean value for week 0 in treated horses. Insulin sensitivity significantly increased (> 2-fold) in treated horses, but glucose effectiveness and net insulin response were not affected. Levothyroxine sodium significantly increased the rate of insulin disposal. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of L-T4 decreases blood lipid concentrations, improves insulin sensitivity, and increases insulin disposal in horses. Levothyroxine sodium may have potential as a treatment for horses with reduced insulin sensitivity.

Animals↗

PubMed2005

Physiologic assessment of blood glucose homeostasis via combined intravenous glucose and insulin testing in horses.

OBJECTIVE: To characterize the physiologic response to i.v. bolus injection of glucose and insulin for development of a combined glucose-insulin test (CGIT) in horses. ANIMALS: 6 healthy mares and 1 mare each with pituitary adenoma and urolithiasis. PROCEDURE: Horses were given a CGIT (glucose, 150 mg/kg; insulin, 0.1 U/kg); results were compared with a singular i.v. glucose tolerance test (GTT; 150 mg/kg) and a singular i.v. insulin sensitivity test (IST; 0.1 U/kg). Healthy horses were also given a CGIT after receiving xylazine and undergoing stress. RESULTS: Physiologically, the CGIT resulted in a 2-phase curve with positive (hyperglycemic) and negative (hypoglycemic) portions; the positive phase came first (250% of baseline at 1 minute). The descending segment declined linearly to baseline by approximately 30 minutes and to a nadir at 58% of baseline by 75 minutes. After a 35-minute valley, a linear ascent to baseline began. Addition of insulin in the CGIT increased glucose utilization by approximately 4.5 times during the positive phase but not during the negative phase. The diseases' effects and experimental inhibition of insulin secretion with xylazine and stress were detectable by use of the 2 phases of the CGIT. Only a single positive phase resulted from the GTT and a single negative phase from the IST CONCLUSIONS AND CLINICAL RELEVANCE: The CGIT resulted in a consistent, well-defined glycemia profile, which can be disrupted experimentally or by a disease process. The CGIT has clinical potential because it provides integrated information and more information than either the singular GTT or IST.

Animals↗

PubMed2005

Effects of dietary oils on the development of gastric ulcers in mares.

OBJECTIVE: To assess antiulcerogenic properties of 3 dietary oils. ANIMALS: 8 healthy adult mares. PROCEDURE: A protocol to induce gastric ulcers was used and included 240 mL of water plus corn oil, refined rice bran oil, or crude rice bran oil administered each day for 6 weeks according to a 4 x 4 Latin square randomized crossover design with 5-week washout intervals. A 7-day alternating feed deprivation period was included between weeks 5 and 6. Omeprazole was administered daily for the last 14 days of each washout interval. Endoscopic examinations of the stomach were performed at 0, 5, and 6 weeks, and the number (0 to 4 scale) and severity (0 to 5 scale) of ulcers were scored. Gastric fluid was collected at 0 and 5 weeks. RESULTS: Median body weight significantly increased by 29 kg (range, 10 to 50 kg). Mean +/- SE gastric fluid pH significantly decreased from 4.9 +/- 0.4 to 3.1 +/- 0.3 over 5 weeks, and total volatile fatty acid concentration significantly decreased over time. Mean +/- SE severity of nonglandular ulcers significantly increased from 0.4 +/- 0.1 to 1.2 +/- 0.2 over 5 weeks. Nonglandular ulcers significantly increased in number (mean +/- SE, 1.3 +/- 0.2 to 3.0 +/- 0.2) and severity (mean +/- SE, 1.2 +/- 0.2 to 2.6 +/- 0.2) during the 7-day alternating feed deprivation period. No effects of treatment were detected. CONCLUSIONS AND CLINICAL RELEVANCE: In this model dietary oils did not prevent gastric ulcers from forming in the nonglandular portion of the stomach of horses.

Animals↗

PubMed2004

Vertebral malformation, syringomyelia, and ventricular septal defect in a dromedary camel (Camelius dromedarius).

An occipitoatlantoaxial malformation and ventricular septal defect (VSD) were diagnosed in a 36-hour-old female camel. Physical examination revealed a firm protrusion of the dorsal aspect of the atlas and axis, tilting of the head to the left, and a grade V/VI systolic murmur. Neurological examination revealed proprioceptive deficits and ataxia of all 4 limbs. Radiographic examination and necropsy demonstrated malformation, fusion of the atlas to the occiput and hypoplasia of the dens of the axis, and subluxation of the atlantoaxial joint. Dorsoventral laxity of the atlantoaxial joint was also present, with compression of the cervical spinal cord. A 1.5-cm-diameter VSD was observed also. Histopathologic examination of the cervical spinal cord revealed a cavity extending from the level of the first to fourth cervical segment, dorsal to the central canal, 5 cm long and 1-2 mm in diameter. The cells around the cavity were positive for glial fibrillary acidic protein and sporadically positive for vimentin. This cavitary structure was consistent with syringomyelia, which was lined by glial cells, surrounded by edematous white matter with Wallerian-like degeneration and with neuronal necrosis in the adjacent dorsal horns.

Animals↗

PubMed2003

Effect of hypothyroidism on kinetics of metabolism of very-low-density lipoprotein in mares.

OBJECTIVE: To compare kinetics of the metabolism of very-low-density lipoprotein (VLDL) apolipoprotein B (apoB) before and after thyroidectomy in mares. ANIMALS: 5 healthy adult mares. PROCEDURE: Thyroidectomy was performed in euthyroid mares. Kinetics of VLDL apoB metabolism were measured before and after thyroidectomy by use of a bolus IV injection of 5,5,5-2H3 (98%) leucine (5 mg/kg) and subsequent isolation of labeled amino acid from plasma and VLDL. Labeled leucine was quantified by use of gas chromatography-mass spectrometry. Production rate (PR), delay time, and fractional catabolic rate (FCR) were calculated for the 2 forms of equine VLDL, apoB-48 VLDL, and apoB-100 VLDL. Plasma lipid concentrations were measured, and VLDL composition was determined. RESULTS: Physical appearance of horses was not altered by thyroidectomy. Significantly lower mean blood concentrations of thyroid hormones and non-esterified fatty acids were detected following thyroidectomy. Mean percentage of free cholesterol in VLDL was significantly higher after thyroidectomy. Mean plasma VLDL concentration or kinetics of apoB-48 or apoB-100 were not significantly altered by thyroidectomy. Mean +/- SEM PR was significantly lower (8.70 +/- 1.61 mg/kg/d) and mean delay time significantly longer (1.58 +/- 0.12 hours) for apoB-48 VLDL in euthyroid mares, compared with values for thyroidectomized mares (16.15 +/- 2.24 mg/kg/d and 0.93 +/- 0.10 hours, respectively). CONCLUSIONS AND CLINICAL RELEVANCE: Hypothyroidism did not significantly alter plasma VLDL concentrations or kinetics of VLDL apoB metabolism. Metabolism of apoB-48 VLDL differed significantly from that of apoB-100 VLDL in euthyroid mares.

Animals↗

PubMed2003

Effects of hypothyroidism and withholding of feed on plasma lipid concentrations, concentration and composition of very-low-density lipoprotein, and plasma lipase activity in horses.

OBJECTIVE: To evaluate selected concentrations of blood lipids and lipase activities in euthyroid and hypothyroid horses deprived of feed for 96 hours. ANIMALS: 4 healthy adult mares and 4 thyroidectomized adult mares. PROCEDURE: Horses were deprived of feed for 96 hours. Blood samples were collected at 24-hour intervals and analyzed to determine concentrations of non-esterified fatty acid (NEFA), triglyceride (TG), total cholesterol (TC), and very-low-density lipoprotein (VLDL) as well as composition of VLDL. Plasma lipase activities were measured after feed was withheld for 96 hours and 12 days after resumption of feeding. RESULTS: Time significantly affected plasma NEFA, VLDL, TG, and TC concentrations in both groups of horses. During the 96-hour period, mean plasma concentrations of NEFA and VLDL increased 10-fold in euthyroid horses and increased 5-fold and 9-fold, respectively, in hypothyroid horses. Mean plasma TG concentrations increased 8-fold in both groups, and plasma TC concentrations significantly increased by 33 and 30%, respectively. Composition of VLDL was significantly affected by feed deprivation in euthyroid horses. Activities of lipoprotein lipase and hepatic lipase were significantly higher in feed-deprived horses. Activity of hepatic lipase was significantly lower in hypothyroid horses than in euthyroid horses. CONCLUSIONS AND CLINICAL RELEVANCE: Hypothyroidism did not significantly alter the magnitude of the response of blood lipids to feed deprivation. Thyroid hormones may reduce variability in blood lipid concentrations but do not determine susceptibility to hyperlipemia. Hypothyroidism does not appear to be a factor in the pathogenesis of hyperlipemia in horses.

Animals↗

PubMed2002

Surgical management of a ureteral defect with ureterorrhaphy and of ureteritis with ureteroneocystostomy in a foal.

A 2-day-old male foal developed uroperitoneum. Initial exploration of the abdomen via ventral midline celiotomy failed to localize the source of uroperitoneum. Bilateral nephropyelocentesis and antegrade urography were performed, and a defect in the right ureter and stenosis of the left ureter were identified. With the foal in dorsal recumbency in the Trendelenburg position, ureterorrhaphy was performed on the right ureter. After ureterorrhaphy, a ureteral catheter was maintained as a stent. The stenotic left ureter was transected, and ureteroneocystostomy was performed using a drop-in mucosal apposition technique. The ureteral catheter was removed 26 days after surgery. Histopathologic findings suggested that ureteritis of unknown origin was a possible initiating factor for stenosis of the left ureter. The drop-in technique for ureteroneocystostomy may be used successfully for ureteral transposition in horses. Ureterorrhaphy combined with the use of a ureteral stent may be used to repair ureteral defects in foals.

Animals↗

PubMed2002

Equine thyroid dysfunction.

Hypothyroidism is the most common type of thyroid gland dysfunction reported in horses. Primary, secondary, and tertiary causes of hypothyroidism are discussed. Equine hypothyroidism remains a controversial endocrine disorder because extrathyroidal factors, including the administration of drugs and systemic diseases, affect serum triiodothyronine (T3) and thyroxine (T3) concentrations in horses. Accurate diagnosis of hypothyroidism therefore requires assessment of the hypothalamic-pituitary-thyroid axis. Diagnostic procedures for evaluating thyroid gland function are outlined and results of studies utilizing experimental models are discussed.

Animals↗

PubMed2002

Effect of withholding feed on concentration and composition of plasma very low density lipoprotein and serum nonesterified fatty acids in horses.

OBJECTIVE: To measure and compare the concentration and composition of very low-density lipoprotein (VLDL) in plasma and selected lipids in serum of horses fed mixed grass hay ad libitum or denied feed for 36 hours. ANIMALS: 4 healthy adult mares. PROCEDURE: Mares were either fed mixed grass hay ad libitum or denied feed for 36 hours beginning at 8:00 AM. Blood samples were collected every 2 hours during the study period and analyzed for nonesterified fatty acid (NEFA), triglyceride (TG), VLDL, and glucose concentrations and composition of VLDL. RESULTS: Withholding feed significantly increased mean serum concentrations of NEFA. By 36 hours, a 16-fold increase in mean serum NEFA concentration and 2-fold increase in mean plasma VLDL concentration, compared with baseline values, were detected. Mean plasma TG concentrations significantly increased with time in feed-deprived horses. Significantly lower overall mean plasma glucose concentrations were detected in feed-deprived horses. Mean percentage of protein in VLDL was significantly lower in feed-deprived horses. Plasma VLDL concentrations varied widely among horses in response to withholding feed. Plasma TG and VLDL concentrations remained unaltered in 2 horses. CONCLUSIONS AND CLINICAL RELEVANCE: Withholding feed significantly increases blood lipid concentrations in horses, but individual horses respond differently. Serum NEFA concentrations were increased in all 4 horses denied feed, indicating mobilization of tissue triglyceride stores. Variation in plasma VLDL concentration in response to withholding feed suggests that its metabolism is strongly influenced by other, as yet undetermined, factors in horses. Differences in the plasma VLDL concentrations among horses in response to withholding feed may be used as an indication of susceptibility to the hyperlipemic syndrome of Equidae.

Animals↗

PubMedDate not supplied

Quantitative assessment of hepatic function by means of 99mTc-mebrofenin in healthy horses.

99mTc-mebrofenin is used in humans and small animals to assess hepatic function. This study was undertaken to measure hepatic clearance of 99mTc-mebrofenin in healthy horses and to determine whether feed deprivation and increased serum total bilirubin (TBIL) concentration alter 99mTc-mebrofenin clearance. Plasma clearance of 99mTc-mebrofenin was determirned in 7 healthy horses at 0, 48, and 96 hours of feed withholding. Serum TBIL and nonesterified fatty acid (NEFA) concentrations were measured every 24 hours. 99mTc-mebrofenin (4.16 +/- 0.62 mCi, mean +/- SD) was injected into a jugular vein, and blood samples were retrieved from the contralateral jugular vein. A plasma time-activity curve of 99mTc-mebrofenin was generated, from which the area under the curve (AUC) and the T1/2 of the fast-phase (T1/2) and slow-phase (T1/2f) were calculated. Mean +/- SD AUC was 17,700 +/- 4,257, 18,616 +/- 8,078, and 16,168 +/- 6,031 counts per minute (cpm) at 0, 48, and 96 hours, respectively; mean +/- SD T1/2f was 2.80 +/- 0.38 minutes, 3.52 +/- 1.46 minutes, and 3.82 +/- 1.29 minutes at 0, 48, and 96 hours, respectively; median T1/2s was 63.9, 49.2, and 45.8 minutes at 0, 48, and 96 hours, respectively. No difference was detected between the values of AUC, T1/2f, and T1/2s at 0, 48, and 96 hours. There was a significant increase in TBIL with fasting, with a mean +/- SD of 6.3 +/- 1.3 mg/dL at 26 hours. NEFAs increased, reaching a plateau at 48 hours (650 +/- 152 micromol/L). Plasma TBIL concentrations did not correlate with AUC or T1/2s but correlated weakly with T1/2f (r = 0.50). Plasma NEFA concentrations did not correlate with AUC, T1/2s, or T1/2f values. This study suggests that 99mTc-mebrofenin plasma clearance is not affected by feed withholding and that hyperbilirubinemia associated with feed withholding does not affect the hepatic extraction efficiency of this radiopharmaceutical.

Aniline Compounds↗

PubMedDate not supplied

Effects of intravenously administrated omeprazole on gastric juice pH and gastric ulcer scores in adult horses.

The study was performed to evaluate the efficacy of omeprazole powder in sterile water, administered intravenously, on gastric juice pH in adult horses with naturally occurring gastric ulcers. Omeprazole (0.5 mg/kg, IV) was administered once daily for 5 days to 6 adult horses with gastric ulcers. Gastric juice was aspirated through the biopsy channel of an endoscope and pH was measured before and 1 hour after administration of omeprazole on day 1, and then before and after administration of omeprazole on day 5. Gastric ulcer scores were recorded on day 1 before administration of omeprazole and on day 5, 23 hours after the 4th daily dose. Gastric juice pH and ulcer scores were compared between the times. When compared with the pre-injection value (2.01 +/- 0.42), mean +/- SD gastric juice pH was significantly higher when measured 1 hour after administration of the initial dose (4.35 +/- 2.31), and before (5.27 +/- 1.74) and 1 hour after (7.00 +/- 0.25) administration of omeprazole on day 5. Nonglandular gastric ulcer number score significantly decreased from a mean +/- SD of 3.2 +/- 0.80 to 2.0 +/- 1.1, but nonglandular gastric ulcer severity score remained the same. Few glandular ulcers were seen in the study, and scores did not change. Because of its potent and long duration of action on gastric juice pH, this intravenous formulation of omeprazole may show promise for treatment of equine gastric ulcer syndrome (EGUS) in horses with dysphagia, gastric reflux, or other conditions that restrict oral intake of omeprazole paste. Aspiration of gastric juice and measurement of pH can be of use to determine whether the desired pH > 4.0 has been reached after omeprazole treatment.

Animals↗

PubMedDate not supplied

Evaluation of the combined dexamethasone suppression/ thyrotropin-releasing hormone stimulation test for detection of pars intermedia pituitary adenomas in horses.

BACKGROUND: A combined dexamethasone (DEX) suppression/thyrotropin-releasing hormone (TRH) test (DEX/TRH test) has been developed to evaluate horses for presence of a pars intermedia pituitary adenoma (PIPA), but to the authors' knowledge, the accuracy of this test has not been previously determined. HYPOTHESIS: The sensitivity and specificity of the DEX/TRH test can be determined by comparing test results with histopathologic examination findings. ANIMALS: Age of 42 horses of various breeds ranged from 2 to 33 years. METHODS: Plasma cortisol concentration was measured before and 24 hours after IV administration of 40 microg of DEX/kg of body weight, and before and 30 minutes after IV administration of 1 mg of TRH that had been given 3 hours after the injection of DEX. Results of the DEX/TRH test were considered positive if either the plasma cortisol concentration exceeded 10 ng/mL 24 hours after DEX administration, or if the change in plasma cortisol concentration 30 minutes after injection of TRH was > or = 66% above the 3-hour baseline. Diagnosis of PIPA was determined by histologic examination of the pituitary gland. RESULTS: PIPA was detected in 17 of 42 (40%) horses. The DEX/TRH test had sensitivity, specificity, positive predictive value, and negative (NPV) predictive value of 88, 76, 71, and 90%, respectively. CONCLUSIONS AND CLINICAL IMPORTANCE: The combined DEX/TRH test was more sensitive than either of its component tests and had a high NPV, but was not as specific as the TRH component alone (92%). The DEX/TRH test should be used to screen older horses for PIPA.

Animals↗