Kent R. Refsal

Developmental Programming: Impact of Excess Prenatal Testosterone on Intrauterine Fetal Endocrine Milieu and Growth in Sheep

Prenatal testosterone excess in sheep leads to reproductive and metabolic disruptions that mimic those seen in women with polycystic ovary syndrome. Comparison of prenatal testosterone-treated sheep with prenatal dihydrotestosterone-treated sheep suggests facilitation of defects by androgenic as well as androgen-independent effects of testosterone. We hypothesized that the disruptive impact of prenatal testosterone on adult pathology may partially depend on its conversion to estrogen and consequent changes in maternal and fetal endocrine environments. Pregnant Suffolk sheep were administered either cottonseed oil (control) or testosterone propionate in cottonseed oil (100 mg, i.m. twice weekly), from Day 30 to Day 90 of gestation (term is ∼147 d). Maternal (uterine) and fetal (umbilical) arterial samples were collected at Days 64–66, 87–90, and 139–140 (range; referred to as D65, D90, and D140, respectively) of gestation. Concentrations of gonadal and metabolic hormones, as well as differentiation factors, were measured using liquid chromatography/mass spectrometer, radioimmunoassay, or ELISA. Findings indicate that testosterone treatment produced maternal and fetal testosterone levels comparable to adult males and D65 control male fetuses, respectively. Testosterone treatment increased fetal estradiol and estrone levels during the treatment period in both sexes, supportive of placental aromatization of testosterone. These steroidal changes were followed by a reduction in maternal estradiol levels at term, a reduction in activin A availability, and induction of intrauterine growth restriction in D140 female fetuses. Overall, our findings provide the first direct evidence in support of the potential for both androgenic as well as estrogenic contribution in the development of adult reproductive and metabolic pathology in prenatal testosterone-treated sheep.

Blood Arginine Vasopressin, Adrenocorticotropin Hormone, and Cortisol Concentrations at Admission in Septic and Critically Ill Foals and their Association with Survival

BACKGROUND Sepsis is an important cause for neonatal foal mortality. The hypothalamic-pituitary-adrenal axis (HPAA) responses to sepsis are well documented in critically ill humans, but limited data exist in foals. The purpose of this study was to evaluate the HPAA response to sepsis in foals, and to associate these endocrine changes with survival. HYPOTHESIS Blood concentrations of arginine vasopressin (AVP), adrenocorticotropin hormone (ACTH), and cortisol will be higher in septic foals as compared with sick nonseptic and healthy foals. The magnitude of increase in hormone concentration will be negatively associated with survival. ANIMALS Fifty-one septic, 29 sick nonseptic, and 31 healthy foals of < or =7 days of age were included. METHODS Blood was collected at admission for analysis. Foals with positive blood culture or sepsis score > or =14 were considered septic. Foals admitted with disease other than sepsis and healthy foals were used as controls. AVP, ACTH, and cortisol concentrations were measured using validated immunoassays. RESULTS AVP, ACTH, and cortisol concentrations were increased in septic foals. Septic nonsurvivor foals (n = 26/51) had higher plasma ACTH and AVP concentrations than did survivors (n = 25/51). Some septic foals had normal or low cortisol concentrations despite increased ACTH, suggesting relative adrenal insufficiency. AVP, ACTH, and cortisol concentrations were higher in sick nonseptic foals compared with healthy foals. CONCLUSIONS AND CLINICAL IMPORTANCE Increased plasma AVP and ACTH concentrations in septic foals were associated with mortality. Several septic foals had increased AVP : ACTH and ACTH : cortisol ratios, which indicates relative adenohypophyseal and adrenal insufficiency.

Primary hyperaldosteronism in two cats.

A condition of primary hyperaldosteronism resulting from an adrenal tumor in two cats is presented and was characterized by hypertension, hypokalemia, inappropriate kaliuresis, low normal plasma renin activity, and markedly increased serum aldosterone concentration. One of the two cats underwent a laparotomy, and in this case hypertension and hypokalemia resolved following the removal of an adrenal tumor.

Endocrine profiles in cows with ovarian cysts experimentally induced by treatment with exogenous estradiol or adrenocorticotropic hormone

Abstract The objectives of this study were to 1) induce formation of ovarian cysts in dairy cows and identify accompanying changes in luteinizing hormone (LH) and ovarian steroids and 2) characterize profiles of gonadotropin and sex steroid secretion in cows with experimentally induced ovarian cysts. Nonlactating dairy cows, synchronized to be in late diestrus, received either a placebo, 10 mg estradiol-17β, or multiple treatments of 100 IU adrenocortropic hormone (ACTH) gel. Jugular blood was drawn every 4 h for 8 d and palpation per rectum performed daily for 20 d. Ovarian cysts formed in 0 of 5 control, 2 of 5 estradiol-treated, and 2 of 5 ACTH-treated cows. Estradiol treatment resulted in synchronous luteal regression with a preovulatory surge-like release of LH occurring before luteal regression was complete. At 5 to 8 d after administration of estradiol, cows were either identified as having an ovarian cyst or had a spontaneous preovulatory LH surge that was followed by ovulation. Preovulatory surges of LH did not occur after luteal regression in ACTH-treated cows, with ovarian cysts detected within 2 to 3 d. There was great variation in basal endocrine profiles in cows with experimentally induced cysts. After administration of exogenous estradiol (1 mg), only one of four cows with induced cysts responded with a preovulatory surge-like release of gonadotropins.

Serum insulin-like growth factor-I concentration in cats with diabetes mellitus and acromegaly

BACKGROUND Serum insulin-like growth factor-I (IGF-I) has been used in place of serum growth hormone quantification for identifying acromegaly in diabetic cats. The utility of IGF-I as a screening test for acromegaly has not been critically evaluated. This retrospective study was performed to evaluate the usefulness of serum IGF-I concentration for identifying acromegaly. HYPOTHESIS Serum IGF-I is a useful screening test for acromegaly in diabetic cats. ANIMALS A review was made of the medical records of 74 diabetic cats that had serum IGF-I quantified. The diabetes was classified as well controlled (15 cats), poorly controlled because of problems with the insulin treatment regimen, concurrent disease, or both (40), or poorly controlled with clinical findings consistent with acromegaly (19). METHODS A review of medical records was made. RESULTS Serum IGF-I concentration was significantly (P < .0001) increased in acromegalic diabetic cats, compared with well-controlled and poorly controlled diabetic cats. Sensitivity and specificity for serum IGF-I concentration were 84% (95%/ confidence interval [CI] = 60.4-96.6%) and 92% (95% CI = 81.3-97.2%), respectively. There was no significant correlation between serum IGF-I concentration and duration of insulin treatment (r = 0.23, P = .089), insulin dosage (r = 0.14, P = .30), age (r = 0.16, P = .12), and pituitary volume (r = 0.40, P = .11), but a modest correlation was found between serum IGF-I concentration and body weight (r = 0.48, P < .0001). CONCLUSIONS AND CLINICAL IMPORTANCE Results support the use of serum IGF-I concentration as a screening test for acromegaly in diabetic cats that have clinical findings supportive of the disease.

Hypercalcemia and Renal Failure: Etiology, Pathophysiology, Diagnosis, and Treatment

Hypercalcemia is a frequent disorder of calcium metabolism in dogs and cats. Hypercalcemia-induced alterations in renal function and morphology are linked to many of the clinical manifestations observed in hypercalcemic patients. Since many renal effects induced by hypercalcemia are potentially reversible, early recognition and characterization of the problem facilitates rapid therapeutic intervention.

Basal and estradiol-induced release of gonadotropins in dairy cows with naturally occurring ovarian cysts

A study was conducted to identify relationships between serum sex steroid concentrations and release of gonadotropins in dairy cows with ovarian cysts. Cows with ovarian cysts were grouped according to sex steroid profiles as being under estrogenic (n = 6) or low steroid (n = 6) influence. All cows were submitted to a sampling and treatment protocol to 1) record basal pulsatile release of gonadotropins and 2) determine whether luteinizing hormone (LH) or follicle stimulating hormone (FSH) was released after sequential administration of exogenous estradiol and gonadotropin releasing hormone (GnRH) treatments were given 30 h apart. Basal LH was higher in the estrogen-influence group (P < 0.05). There were no differences between groups in basal FSH concentrations or frequency and amplitude of pulsatile LH or FSH release. Only one of the twelve cows, an individual from the low steroid group, had a preovulatory-like surge of gonadotropins after exogenous estradiol. All cows released LH and FSH in response to GnRH treatment, with no differences between groups. These results show that 1) there is considerable variation in pulsatile release of gonadotropins in cows with ovarian cysts, even among individuals with similar sex steroid profiles, and 2) suggest that a factor in the persistence, and perhaps initiation, of the cystic condition is refractoriness to the positive feedback effect of estradiol on gonadotropin release.

Relationship among Serum Creatinine, Serum Gastrin, Calcium- phosphorus Product, and Uremic Gastropathy in Cats with Chronic Kidney Disease

Background Chronic kidney disease (CKD) in cats is associated with gastrointestinal signs commonly attributed to uremic gastropathy. Consequently, patients often are treated with antacids and gastrointestinal protectants. This therapeutic regimen is based on documented gastric lesions in uremic humans and dogs, but the nature and incidence of uremic gastropathy in cats are unknown. Hypothesis/Objectives Evaluate uremic gastropathy in CKD cats to facilitate refinement of medical management for gastrointestinal signs. Animals Thirty‐seven CKD cats; 12 nonazotemic cats Methods Stomachs were evaluated for the presence of classic uremic gastropathy lesions. Histopathologic lesions were compared with serum creatinine concentrations, calcium‐phosphorus product (CPP), and serum gastrin concentrations. Results Gastric ulceration, edema, and vascular fibrinoid change were not observed. The most important gastric lesions in CKD cats were fibrosis and mineralization. Sixteen CKD cats (43%) had evidence of gastric fibrosis of varying severity and 14 CKD cats (38%) had gastric mineralization. CKD cats were more likely to have gastric fibrosis and mineralization than nonazotemic controls (P = .005 and P = .021, respectively). Only cats with moderate and severe azotemia had gastric mineralization. CPP was correlated with disease severity; severely azotemic CKD cats had significantly higher CPP when compared with nonazotemic controls, and to mildly and moderately azotemic cats (P < .05). Gastrin concentrations were significantly higher in CKD cats when compared with nonazotemic controls (P = .003), but increased concentrations were not associated with gastric ulceration. Conclusions and Clinical Importance Uremic gastropathy in CKD cats differs from that described in other species and this difference should be considered when devising medical management.

An Investigation of the Action of Neutral Protamine Hagedorn Human Analogue Insulin in Dogs with Naturally Occurring Diabetes Mellitus

BACKGROUND Neutral Protamine Hagedorn human analogue insulin (Humulin N) is commonly used for treatment of canine diabetes mellitus (DM). However, blood glucose and serum insulin concentrations in Humulin N-treated dogs with naturally occurring DM have not been reported. OBJECTIVE To investigate blood glucose and serum insulin concentrations in the clinical setting of client-owned Humulin N-treated dogs with naturally occurring, well-regulated DM. ANIMALS Ten client-owned dogs with naturally occurring, well-regulated DM. METHODS In this clinical study, blood glucose and serum insulin concentrations were measured when dogs received food and insulin (T(0)), at approximately every half hour for the next 2 hours, and then approximately every 2 hours for an additional 8 hours. Insulin duration of action was defined as the number of hours from T(0) to the lowest blood glucose concentration and until blood glucose concentration returned to an interpolated value of 70% of basal blood glucose concentration (Glucose(b)). RESULTS Mean percent of insulin-induced blood glucose suppression was 49.9 +/- 17.1% (median, 46%; range, 29-78%). Insulin duration of action ranged from 4 to 10 hours. Blood glucose concentration increased initially and returned to Glucose(b) within 0.6-2.2 hours after T(0) in 5 dogs. This initial blood glucose surge then was followed by blood glucose suppression in all 5 dogs. CONCLUSIONS AND CLINICAL IMPORTANCE These results suggest that Humulin N administered SC twice daily is an effective mode of treatment for dogs with naturally occurring DM. Postprandial hyperglycemia is present in some well-regulated diabetic dogs treated with Humulin N.

Measurement of Free Thyroxine Concentration in Horses by Equilibrium Dialysis

The purpose of the study reported here was to validate measurement of free thyroxine (fT4) concentration in equine serum by equilibrium dialysis (fT4D), and to compare values with fT4 concentration measured directly and with total T4 (TT4) concentration. The fT4D, fT4, and TT4 concentrations were measured over a range of values in euthyroid horses and horses made hypothyroid by administration of propylthiouracil (PTU). Concentrations of fT4D (<1.8-83 pmol/L) were consistently higher than those of fT4 (<1-40 pmol/L). There was a significant (P < .001) regression of fT4D on fT4 in 503 samples from normal horses (y = 2.086x - 0.430). In baseline samples from 71 healthy euthyroid horses, fT4 concentration ranged from 6-21 pmol/L (median, 11 pmol/L; 95% confidence interval [CI]10.5-11.8 pmol/L), and fT4D concentration ranged from 7-47 pmol/L (median, 22 pmol/L; 95% CI 20.9-25.1 pmol/L). Free T4D, fT4, and TT4 concentrations were also measured in 34 ill horses. Horses consuming PTU and ill horses had significantly (P < .05) lower serum concentration of TT4, fT4, and fT4D than did clinically normal, healthy horses. If serum samples from ill horses were further subdivided into samples from horses that lived and samples from horses that died, fT4D concentration was not significantly different in ill horses that lived, compared with that in healthy horses, whereas fT4 concentration was still significantly decreased in ill horses that died (P < 0.001). We conclude that measurement of fT4 concentration by equilibrium dialysis is a valid technique in the horse, and its use may provide improved ability to distinguish nonthyroidal illness syndrome from hypothyroidism in that species.