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SUMMARY

A radioimmunoassay for measurement of midmolecule parathyroid hormone (pth) concentration in serum from dogs was validated for use on serum from cats. The assay detected an increase in serum concentration of pth after iv infusion of Na2 edta in healthy cats. Infusion of calcium chloride caused a decrease in measured pth. Accuracy of the assay was demonstrated by quantitative recovery of a feline parathyroid gland extract added to pooled feline sera. Mean interassay and intra-assay coefficients of variation were 0.13 and 0.07, respectively. Sensitivity of the assay was 0.1 ng of pth/ml. The median pth concentration measured in 40 adult cats was 3.5 ng/ml, with a range of 1.16 to 11.0 ng/ml.

Free access
in American Journal of Veterinary Research

Summary

Hyperlipemic serum and plasma samples often are received by clinical laboratories for endocrinologic analysis by radioimmunoassay. We designed a study to determine what effect, if any, hyperlipemia has on estimation of lipid-soluble hormone concentrations determined by solid-phase radioimmunoassays. Progesterone, testosterone, thyroxine, and cortisol concentrations were determined in canine plasma and serum with various degrees of lipemia. Samples of serum, heparinized plasma, and edta-treated plasma were obtained from blood collected from 4 female and 4 male Beagles by use of evacuated tubes. To induce hyperlipemia in vitro, iv fat emulsion was diluted in deionized water to produce 0 (water only), 33, 67, or 100% mixtures. Twenty microliters of each mixture then was added to the subsamples of serum and plasma from each dog. Hormone concentrations were determined, using validated radioimmunoassays. Triglyceride concentrations were determined by enzymatic assay. Addition of iv fat emulsion in vitro was an accurate and reproducible means of altering triglyceride concentrations in the samples. Triglyceride concentrations as high as 700 mg/dl had no effect on radioimmunoassays for progesterone, testosterone, and thyroxine in serum, heparinized plasma, or edta-treated plasma. Addition of 100% (but not 33 or 67%) fat emulsion reduced the mean cortisol concentration in heparinized plasma by 12% (P < 0.05). This severe hyperlipemia did not affect quantification of cortisol in serum or edta-treated plasma.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine the effect of immunization with bovine luteinizing hormone receptor (LH-R) on ovarian function of cats.

Animals—9 adult female domestic cats.

Procedure—7 cats were immunized with 0.5 mg of LH-R encapsulated in a silastic subdermal implant (3 × 10 mm); 2 served as control cats. Receptors had 80% specific binding to 125I-human chorionic gonadotropin with a binding capacity of 2,682 pM/mg. Cats received booster injections of LH-R. Cats were induced to ovulate with luteinizing hormone (LH) releasing hormone on day 345. Samples of venous blood and vaginal cells were collected through day 395. Observation of estrus behavior continued until day 516. Serum concentrations of estradiol, progesterone, thyroid gland hormones, LH, and LH-R antibody were determined.

Results—LH-R antibody was detected in the sera of immunized cats within 21 days after implantation. Detection of LH-R antibody was associated with suppression of serum progesterone to ≤ 0.5 ng/mL during the study period, compared with concentrations of 5 to 10 ng/mL in control cats. Immunized cats did not display signs of estrus. Release of LH after administration of LH releasing hormone indicated an intact hypothalamic-pituitary axis but poor corpus luteum function. Serum estradiol concentrations remained between 30 to 40 pg/mL in immunized and control cats. With the decrease antibody titers, hormone concentrations returned to a pattern consistent with that during fertility.

Conclusions and Clinical Relevance—Active immunization with LH-R suppressed corpus luteum function in cats. The effect was reversible. An LH-R-based antifertility vaccine may have clinical application in other vertebrates. (Am J Vet Res 2003;64:292–298)

Full access
in American Journal of Veterinary Research

Abstract

Objective

To determine whether the urine cortisol-to-creatinine ratio (UCCR) could replace the ACTH stimulation test in monitoring effectiveness of mitotane induction treatment in dogs with pituitary-dependent hyperadrenocorticism (PDH).

Animals

15 dogs with PDH.

Procedure

All 15 dogs were given an induction dose of mitotane (o, p'-DDD: 35 to 50 mg/kg of body weight/d) for 3 to 14 days. During the induction period, free-catch morning urine samples were collected for determination of UCCR, followed by ACTH stimulation testing, every other day. Treatment response was divided into 3 categories: well-controlled PDH (post-ACTH serum cortisol concentration ≥ 28 nmol/L but ≤ 138 nmol/L), deficient cortisol secretion (post-ACTH serum cortisol concentration < 28 nmol/L), and excess cortisol secretion (post-ACTH serum cortisol concentration > 138 nmol/L).

Results

The linear relation between UCCR and post-ACTH serum cortisol concentration was significant (P < 0.001); however, the prediction intervals surrounding the line were too broad to be clinically useful. The UCCR overlapped among the 3 categories of treatment response. Nevertheless, dogs with PDH receiving mitotane induction treatment and with UCCR > 79 × 10−6 were always classified as having excess cortisol secretion.

Conclusion and Clinical Relevance

The UCCR failed to predict post-ACTH cortisol concentration during mitotane induction treatment sufficiently close to be a clinically reliable indicator of treatment control. Seemingly, however, UCCR > 79 × 10−6 obtained from a dog with PDH during mitotane induction would indicate inadequate adrenal cortex destruction and the need for continued mitotane induction; UCCR ≤ 79 × 10−6 would be inconclusive. (Am J Vet Res 1998;59:258–261)

Free access
in American Journal of Veterinary Research

Abstract

Adrenocortical function was assessed in 27 Beagle pups at 2, 4, 6, 8, 10, and 12 weeks of age by determination of plasma sodium, potassium, and chloride concentrations; serum aldosterone and cortisol concentrations; and plasma ACTH concentrations. Serum cortisol concentration was measured before and 1 and 2 hours after IM administration of 2.2 IU of acth/kg of body weight. Serum progesterone concentration also was determined for all pups at 2, 4, and 6 weeks of age.

Mean baseline cortisol concentration was lower for pups 8 weeks old or younger than for mature dogs. Nevertheless, mean serum ACIH-stimulated cortisol concentration in dogs of all age groups increased into the adult reference range after administration of acth. For pups 4 weeks old or younger, increase in cortisol concentration was maximal at 2 hours after acth administration. However, in pups between 6 and 12 weeks of age, the increase in cortisol concentration was maximal 1 hour after acth administration in about a third of the pups, whereas the remaining pups had peak values at 2 hours.

Mean plasma sodium, potassium, and chloride concentrations for each age group were within the reference ranges established for mature dogs, with the exception of lower mean plasma sodium and chloride concentrations in pups 4 weeks old or younger. Mean serum aldosterone concentration in pups of each age group was substantially higher than the range of aldosterone concentrations for clinically normal mature dogs. Median progesterone concentration was uniformly less than 0.2 ng/ml for all pups 6 weeks old or younger.

The normal endogenous acth concentration and adequate cortisol responses to exogenous acth seen in our pups would support functional pituitary gland and adrenal cortex for cortisol production. The low baseline cortisol concentration observed in the pups of this study may be related to reduced binding of cortisol to plasma proteins, as exists in human infants. The hyponatremia and increased aldosterone concentration may be explained by reduced renal tubular response to aldosterone, as also evidenced in the human infant kidney.

Free access
in American Journal of Veterinary Research

SUMMARY

Forty-four female American Shorthair cats with inflammatory uterine disease or infertility were evaluated. Data collected included age, month of diagnosis, housing, reproductive history, results of bacteriologic culture of uterine specimens, serum concentrations of estrogen, progesterone, and prolactin and histopathologic features of the ovaries and uterus.

Histologically, the ovaries of 19 cats were dominated by active or cystic follicles, whereas 25 cats had luteal-phase ovaries. Of the 25 cats with active corpora lutea, 20 had either recently weaned litters (n = 11) without subsequent exposure to a male cat, or had been housed individually for lengthy periods (n = 9). The finding of active corpora lutea under these circumstances indicates that in queens, ovulation may occur by mechanisms not involving coitus.

Prominent, active corpora lutea on the ovaries were associated with adenomatotic proliferative changes in the superficial and glandular epithelium of the uterus and with myometrial hyperplasia, compared with the uterus of cats with follicular ovaries (P < 0.01).

Serum progesterone concentration ≥ 1.87 ng/ml was consistently associated with luteal-phase ovaries. Serum progesterone values ≤ 0.15 ng/ml were consistently associated with follicular-phase ovaries.

Escherichia coli was the organism most commonly isolated from uterine contents.

Free access
in American Journal of Veterinary Research

Summary

Veterinary diagnostic endocrinology laboratories frequently receive hemolyzed plasma, serum, or blood samples for hormone analyses. However, except for the previously reported harm done by hemolysis to canine insulin, effects of hemolysis on quantification of other clinically important hormones are unknown. Therefore, these studies were designed to evaluate effects of hemolysis on radioimmunoassay of thyroxine, 3,5,3’-triiodothyronine, progesterone, testosterone, estradiol, cortisol, and insulin in equine, bovine, and canine plasma. In the first experiment, hormones were measured in plasma obtained from hemolyzed blood that had been stored for 18 hours. Blood samples were drawn from pregnant cows, male and diestrous female dogs, and male and pregnant female horses. Each sample was divided into 2 equal portions. One portion was ejected 4 times with a syringe through a 20-gauge (dogs, horses) or 22-gauge (cows) hypodermic needle to induce variable degrees of hemolysis. Two subsamples of the blood were taken before the first and after the first, second, and fourth ejections. One sub sample of each pair was stored at 2 to 4 C and the other was stored at 20 to 22 C for 18 to 22 hours before plasma was recovered and stored at —20 C. The second portion of blood from each animal was centrifuged after collection; plasma was recovered and treated similarly as was blood. Concentrations of thyroxine in equine plasma, of 3,5,3’-triiodothyronine, estradiol, and testosterone in equine and canine plasma, and of cortisol in equine plasma were not affected by hemolysis. Storage of bovine blood at either temperature and equine blood at 20 to 22 C caused progesterone concentrations to decrease (P < 0.05); the effect was not enhanced or diminished by hemolysis. Insulin concentration in equine blood decreased (P < 0.05) at both temperatures; this effect was exacerbated by hemolysis. In the second experiment, blood samples from horses and dogs were hemolyzed and plasma was immediately recovered and stored for 18 to 22 hours at 2 to 4 C or 20 to 22 C. Storage of hemolyzed equine plasma did not affect concentrations of progesterone, insulin, or thyroxine at either temperature. Whereas progesterone concentration was not affected in hemolyzed canine plasma, hemolysis decreased (P < 0.05) insulin concentration when plasma was stored at 20 to 22 C. These results emphasize the importance of examining effects of sample collection and handling procedures on hormone stability and the danger of extrapolating results of such studies from one species to another and from one hormone to another.

Free access
in American Journal of Veterinary Research

SUMMARY

Thyroxine (T4), 3,5,3′-triiodothyronine (T3), and cortisol frequently are quantified in canine serum or plasma samples to aid in the diagnosis of hypothyroidism, hypoadrenocorticism, and hyperadrenocorticism. Many laboratories have established reliable references values for concentrations of these hormones in blood of clinically normal animals. However, nonpathologic factors that affect thyroidal and adrenocortical secretion may lead to misinterpretation of test results when values for individual animals are compared with reference values. The objective of the study reported here was to identify effects of age, sex, and body size (ie, breed) on serum concentrations of T3, T4, and cortisol in dogs.

Blood samples were collected from 1,074 healthy dogs, and serum concentrations of the iodothyronines and cortisol were evaluated for effects of breed/size, sex, and age. Mean (± sem) serum concentration of T4 was greater in small (2.45 ± 0.06 μg/dl)- than in medium (1.94 ± 0.04 μg/dl)- or large (2.03 ± 0.03 μg/dl)-breed dogs, the same in females (2.11 ± 0.04 μg/dl) and males (2.08 ± 0.04 μ/dl), and greater in nursing pups (3.04 ± 0.05 μg/dl) than in weanling pups (1.94 ± 0.05 μg/dl), rapidly growing dogs (1.95 ± 0.04 μg/dl), and young adult (1.90 ± 0.06 μg/dl), middle-aged adult (1.72 ± 0.05 μg/dl), or old adult (1.50 ± 0.05 μg/dl) dogs. Dogs > 6 years old had lower mean serum T4 concentration than did dogs of all other ages, except middle-aged adults. Mean serum T3 concentration in medium-sized dogs (1.00 ± 0.01 ng/ml) was greater than that in small (0.90 ± 0.01 ng/ml)- and large (0.88 ± 0.01 ng/ml)-breed dogs. Serum T3 concentration was lowest in nursing (0.85 ± 0.01 ng/ml) and weanling (0.77 ± 0.02 ng/ml) pups, increased in rapidly growing dogs (0.99 ± 0.01 ng/ml) and young adult dogs (1.10 ± 0.04 ng/ml), and decreased slightly in middleaged (0.98 ± 0.02 ng/ml) and old (1.01 ± 0.03 ng/ml) adult dogs. Serum T3 concentration was unaffected by sex. Mean serum cortisol concentration was greater in small (1.06 ± 0.07 μg/dl)- than in large (0.79 ± 0.03 μg/ dl)-breed dogs. Serum from nursing pups (0.57 ± 0.04 μg/ dl) contained less cortisol than did serum from older dogs (mean values ≥ 0.92 μg/dl). Serum cortisol concentration was not different between males and females. These effects of breed/size and age on serum T3, T4, and cortisol concentrations should be considered when evaluating thyroid and adrenocortical functions in dogs.

Free access
in American Journal of Veterinary Research

Summary

Assays were validated for the measurement of urinary concentrations of cortisol and creatinine in domestic ferrets (Mustela putorius furo). Urinary concentrations of cortisol and creatinine and the calculated urinary cortisol:creatinine ratio (UCCR) values were determined for 29 clinically normal female ferrets, 22 clinically normal male ferrets, and 12 ferrets with adrenal gland tumors. The UCCR values for the 51 clinically normal ferrets ranged from 0.04 × 10-6 to 1.66 × 10-6, with a median value of 0.22 × 10-6. The UCCR values were significantly (P ≤ 0.01) higher in the 12 ferrets with adrenal tumors, with a range of 0.5 × 10-6 to 60.13 × 10-6 and a median of 5.98 × 10-6. We concluded that determination of UCCR values was useful in the diagnosis of hyperadrenocorticism associated with adrenal neoplasia in domestic ferrets.

Free access
in Journal of the American Veterinary Medical Association