Adenohypophyseal function in dogs with primary hypothyroidism and nonthyroidal illness.

Background: A recent study of dogs with induced primary hypothyroidism (PH) demonstrated that thyroid hormone deficiency leads to loss of thyrotropin (TSH) hypersecretion, hypersomatotropism, hypoprolactinemia, and pituitary enlargement with large vacuolated "thyroid deficiency" cells that double-stained for growth hormone (GH) and TSH, indicative of transdifferentiation of somatotropes to thyrosomatropes.

Hypothesis: Similar functional changes in adenohypophyseal function occur in dogs with spontaneous PH as do in dogs with induced PH, but not in dogs with nonthyroidal illness (NTI).

Animals: Fourteen dogs with spontaneous PH and 13 dogs with NTI.

Growth hormone excess and the effect of octreotide in cats with diabetes mellitus.

In this prospective study 16 cats with diabetes mellitus were examined for concurrent acromegaly by measuring plasma growth hormone (GH) and insulin-like growth factor-I concentrations, and magnetic resonance imaging (MRI) of the pituitary fossa. Additionally, the effects of octreotide administration on the plasma concentrations of glucose, GH, alpha-melanocyte-stimulating hormone (alpha-MSH), adrenocorticotrophic hormone (ACTH), and cortisol were measured. Five cats were diagnosed with hypersomatotropism.

Functional and morphological changes in the adenohypophysis of dogs with induced primary hypothyroidism: loss of TSH hypersecretion, hypersomatotropism, hypoprolactinemia, and pituitary enlargement with transdifferentiation.

From case studies in humans it is known that primary hypothyroidism (PH) may be associated with morphological and functional changes of the pituitary. There is no insight into the time scale of these changes. In this study, seven beagle dogs were followed up for 3 years after the induction of primary hypothyroidism.

Calcium-stimulation test for the assessment of beta-cell function in cats.

To assess the potential of an intravenous calcium-stimulation test (CST) as an indicator of insulin secretion in cats, indices calculated from CST results were compared with indices of insulin secretion derived from an intravenous glucose tolerance test (ivGTT) and hyperglycaemic glucose clamp (HGC) in 11 healthy, normal glucose tolerant, conscious cats. Intravenous administration of 2.5mg/kg Ca(2+) resulted in a significant increase in plasma free Ca(2+) (P<0.

Insulin sensitivity and beta-cell function in healthy cats: assessment with the use of the hyperglycemic glucose clamp.

A hyperglycemic clamp (HGC) was developed for use in conscious cats. In 21 healthy, normal glucose tolerant cats glucose disposal rate (M), insulin sensitivity (ISI (HGC)), and beta-cell response (I) at arterial plasma glucose of 9 mmol.l (-1) were measured.

Hyperthyroidism due to an intrathoracic tumour in a dog with test results suggesting hyperadrenocorticism.

The elevated urinary corticoid/creatinine ratios of an 11-year-old Jack Russell terrier with polyuria were suppressible in a high-dose dexamethasone suppression test, which was suggestive of pituitary-dependent hyperadrenocorticism. The absence of physical and routine-laboratory changes compatible with hyperadrenocorticism and the relatively high plasma thyroxine concentration were the impetus for additional studies of thyroid and adrenocortical functions. A high plasma thyroxine concentration (62 nmol/l; 5.

Alopecia in pomeranians and miniature poodles in association with high urinary corticoid:creatinine ratios and resistance to glucocorticoid feedback.

The adrenocortical function of pomeranians and miniature poodles with alopecia was tested by serial measurements of the urinary corticoid:creatinine ratio (uccr) and by an oral low-dose dexamethasone suppression test (lddst) and uccr measurements. In most of the dogs there was day-to-day variation in the uccrs of the 10 sequential urine samples, often with values above or below the upper limit of the range of healthy control dogs. In 22 alopecic pomeranians the basal uccrs were significantly higher than in 18 non-alopecic pomeranians, and the values of both groups were significantly higher than those of 88 healthy pet dogs.

Thyrotropin-releasing hormone-induced growth hormone secretion in dogs with primary hypothyroidism.

Primary hypothyroidism in dogs is associated with increased release of growth hormone (GH). In search for an explanation we investigated the effect of intravenous administration of thyrotropin-releasing hormone (TRH, 10 microg/kg body weight) on GH release in 10 dogs with primary hypothyroidism and 6 healthy control dogs. The hypothyroid dogs had a medical history and physical changes compatible with hypothyroidism and were included in the study on the basis of the following criteria: plasma thyroxine concentration < 2 nmol/l and plasma thyrotropin (TSH) concentration > 1 microg/l.

Assessment of thyroid function in dogs with low plasma thyroxine concentration.

Background: Differentiation between hypothyroidism and nonthyroidal illness in dogs poses specific problems, because plasma total thyroxine (TT4) concentrations are often low in nonthyroidal illness, and plasma thyroid stimulating hormone (TSH) concentrations are frequently not high in primary hypothyroidism.

Hypothesis: The serum concentrations of the common basal biochemical variables (TT4, freeT4 [fT4], and TSH) overlap between dogs with hypothyroidism and dogs with nonthyroidal illness, but, with stimulation tests and quantitative measurement of thyroidal 99mTcO4(-) uptake, differentiation will be possible.

Animals: In 30 dogs with low plasma TT4 concentration, the final diagnosis was based upon histopathologic examination of thyroid tissue obtained by biopsy.

Role of progestin-induced mammary-derived growth hormone in the pathogenesis of cystic endometrial hyperplasia in the bitch.

Endogenous progesterone and synthetic progestins may induce hypersecretion of growth hormone (GH) of mammary origin, hyperplastic ductular changes in the mammary gland, and the development of cystic endometrial hyperplasia (CEH) in dogs. It was investigated whether progestin-induced mammary GH plays a role in the pathogenesis of CEH in the bitch. During 1 year, bitches with surgically excised mammary glands and healthy control bitches received medroxyprogesterone acetate (MPA).

Effects of growth hormone secretagogues on the release of adenohypophyseal hormones in young and old healthy dogs.

The effects of three growth hormone secretagogues (GHSs), ghrelin, growth hormone-releasing peptide-6 (GHRP-6), and growth hormone-releasing hormone (GHRH), on the release of adenohypophyseal hormones, growth hormone (GH), adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), luteinising hormone (LH), prolactin (PRL) and on cortisol were investigated in young and old healthy Beagle dogs. Ghrelin proved to be the most potent GHS in young dogs, whereas in old dogs GHRH administration was associated with the highest plasma GH concentrations. The mean plasma GH response after administration of ghrelin was significantly lower in the old dogs compared with the young dogs.

Effect of octreotide on plasma concentrations of glucose, insulin, glucagon, growth hormone, and cortisol in healthy dogs and dogs with insulinoma.

The inhibitory effect of the somatostatin analogue octreotide on the secretion of insulin could be used in the treatment of insulinoma. However, current information on the effectiveness of octreotide in dogs is conflicting. Therefore, the endocrine effects of a single subcutaneous dose of 50 microg octreotide were studied in healthy dogs in the fasting state (n=7) and in dogs with insulinoma (n=12).

Melanotroph pituitary adenoma in a cat with diabetes mellitus.

A 13-year-old male, castrated, crossbred cat was referred for insulin-resistant diabetes mellitus. The cat had a ravenous appetite and a dull coat. Basal urinary corticoid/creatinine ratios were normal.

Vasopressin response to osmotic stimulation in 18 young dogs with polyuria and polydipsia.

Common disorders of water homeostasis leading to polyuria include a variety of endocrine, metabolic, and renal disturbances. After exclusion of most of these conditions, the diagnostic dilemma of differentiating between central diabetes insipidus, primary polydipsia, and nephrogenic diabetes insipidus may remain. Here, we report on 18 young dogs with polyuria that had been present in most cases since the dogs were puppies.

Primary hyperaldosteronism, a mediator of progressive renal disease in cats.

In recent years, there has been renewed interest in primary hyperaldosteronism, particularly because of its possible role in the progression of kidney disease. While most studies have concerned humans and experimental animal models, we here report on the occurrence of a spontaneous form of (non-tumorous) primary hyperaldosteronism in cats. At presentation, the main physical features of 11 elderly cats were hypokalemic paroxysmal flaccid paresis and loss of vision due to retinal detachment with hemorrhages.

Urinary corticoid:creatinine ratios in healthy pet dogs after oral low-dose dexamethasone suppression tests.

Eleven dogs were used in a trial to find a suitable dose of dexamethasone for an oral dexamethasone suppression test for the diagnosis of hyperadrenocorticism. Basal urinary corticoid:creatinine ratios were established in all 11 and then groups of seven were given oral doses of 0.02, 0.

Plasma renin activity and plasma concentrations of aldosterone, cortisol, adrenocorticotropic hormone, and alpha-melanocyte-stimulating hormone in healthy cats.

A pathogenetic role of the renin-angiotensin-aldosterone system has been implicated in cats in both systemic arterial hypertension and hypokalemic myopathy. Yet, measurement of plasma aldosterone concentrations (PACs) and plasma renin activity (PRA) has not unequivocally pointed to hyperaldosteronism as a cause of these conditions. To obtain appropriate reference ranges, this study included a large number (130) of healthy house cats of different breeds without a history of recent illness and plasma concentrations of urea and creatinine below the upper limit of the respective reference ranges.

Urinary aquaporin-2 excretion in dogs: a marker for collecting duct responsiveness to vasopressin.

In humans, the urinary aquaporin-2 (U-AQP2) excretion closely parallels changes in vasopressin (VP) action and has been proposed as a marker for collecting duct responsiveness to VP. This report describes the development of a radioimmunoassay for the measurement of U-AQP2 excretion in dogs. In addition, the localization of AQP2 in the canine kidney was investigated by immunohistochemistry.

Urinary glucocorticoid excretion in the diagnosis of hyperadrenocorticism in ferrets.

Hyperadrenocorticism in ferrets is usually associated with unaltered plasma concentrations of cortisol and adrenocorticotropic hormone (ACTH), although the urinary corticoid/creatinine ratio (UCCR) is commonly elevated. In this study the urinary glucocorticoid excretion was investigated in healthy ferrets and in ferrets with hyperadrenocorticism under different circumstances. In healthy ferrets and in one ferret with hyperadrenocorticism, approximately 10% of plasma cortisol and its metabolites was excreted in the urine.

Pulsatile secretion pattern of vasopressin under basal conditions, after water deprivation, and during osmotic stimulation in dogs.

Measurement of plasma osmolality (Posm) and plasma vasopressin (VP) concentration in response to hypertonicity is regarded as the gold standard for the assessment of VP release in polyuric conditions. Yet the interpretation of the VP curve as a function of Posm may be hampered by the occurrence of VP pulses. To determine whether VP is secreted in a pulsatile fashion in the dog and whether stimulation of VP release changes the secretion pattern of VP, we measured VP at 2-min intervals for 2 h under basal conditions, after 12 h of water deprivation, and during osmotic stimulation with hypertonic saline (20%) in eight healthy dogs.

Morphology of the pituitary gland in ferrets (Mustela putorius furo) with hyperadrenocorticism.

Pituitary tumours are the cause of hyperadrenocorticism in a variety of species, but the role of the pituitary gland in hyperadrenocorticism in ferrets is not known. In this species, the disease is mediated by the action of excess gonadotrophins on the adrenal cortex and is characterized by an excessive secretion of sex steroids. In this study, the pituitary gland of four healthy control ferrets, intact or neutered, and 10 neutered ferrets with hyperadrenocorticism was examined histologically following immunohistochemical labelling for adrenocorticotrophic hormone, alpha-melanocyte-stimulating hormone, growth hormone, thyroid-stimulating hormone, luteinizing hormone, follicle-stimulating hormone, and prolactin.

Somatotroph and corticotroph pituitary adenoma (double adenoma) in a cat with diabetes mellitus and hyperadrenocorticism.

A 9-year-old castrated male European shorthair cat with insulin-resistant diabetes was referred with the preliminary diagnosis of pituitary-dependent hyperadrenocorticism, based on measurements of urinary corticoids. Further studies revealed not only resistance of plasma concentrations of cortisol, adrenocorticotropic hormone (ACTH) and alpha-melanocyte-stimulating hormone (alpha-MSH) to suppression by a low dose of dexamethasone, but also elevated plasma concentrations of growth hormone (GH) and insulin-like growth factor I (IGF-I). Pituitary imaging with dynamic contrast-enhanced computed tomography demonstrated an enlarged pituitary gland and an adenoma.

Dynamic computed tomography of the pituitary gland in dogs with pituitary-dependent hyperadrenocorticism.

Dynamic computed tomography (CT) of the pituitary gland was performed in 55 dogs with pituitary-dependent hyperadrenocorticism (PDH) that underwent transsphenoidal hypophysectomy. On routine contrast-enhanced CT images, microadenomas of the pituitary gland often are indistinguishable from nontumorous pituitary tissue because of isoattenuation. Dynamic CT may allow visualization of these adenomas.