Evaluation of Thyroid‐Stimulating Hormone,Total Thyroxine,and Free Thyroxine Concentrations in Hyperthyroid Cats Receiving Methimazole Treatment

Background

Iatrogenic hypothyroidism (IH) after treatment of hyperthyroidism can impair renal function. No study compared the efficacy of measurement of serum free thyroxine by equilibrium dialysis (fT4ed) or thyroid‐stimulating hormone (TSH) concentrations for monitoring cats receiving methimazole.

Objectives

To (1) compare the ability of total T4 and fT4ed concentrations in conjunction with TSH to define thyroid function in hyperthyroid cats receiving methimazole, (2) determine the prevalence of IH in cats receiving methimazole, and (3) examine the relationship between thyroid axis hormones and serum creatinine concentration.

Animals

One hundred and twenty‐five serum samples from hyperthyroid cats receiving methimazole and total T4 concentrations ≤3.9 μg/dL.

Methods

Total T4, fT4ed, and TSH concentrations were measured to evaluate thyroid status and serum creatinine concentration was measured to assess renal function. A low total T4 or fT4ed concentration in combination with an increased TSH concentration defined IH.

Results

Forty‐one cats (33%) had increased TSH concentrations. Of cats with total T4 and fT4ed concentrations below the reference range, 68% and 73%, respectively, had TSH concentrations above the reference range. Only 18% of cats with a normal TSH concentration had an increased serum creatinine concentrations as compared to 39% of those with increased TSH concentrations (P < .001).

Conclusions

Free T4ed does not identify more cats with potential IH as compared to total T4. The IH prevalence was approximately 20%. Measurement of TSH may be more helpful in indicating that azotemia, if present, is at least in part related to IH. Investigation is needed to define TSH assay utility in identifying possible subclinical IH.     

Spontaneous emission spectrum in double quantum dot devices

A double quantum dot device is a tunable two-level system for electronic energy states. A dc electron current was used to directly measure the rates for elastic and inelastic transitions between the two levels. For inelastic transitions, energy is exchanged with bosonic degrees of freedom in the environment. The inelastic transition rates are well described by the Einstein coefficients, relating absorption with stimulated and spontaneous emission. The most effectively coupled bosons in the specific environment of the semiconductor device used here were acoustic phonons. The experiments demonstrate the importance of vacuum fluctuations in the environment for quantum dot devices and potential design constraints for their use for preparing long-lived quantum states.     

Efficiency of a novel biodegradable pyrolysis liquid-amended mulch in weed control

Agrochemicals and plastics represent a burden on natural ecosystems and there is an urgent need to introduce alternative plant protection measures that have fewer negative impacts on the environment. Replacement of plastic mulches and synthetic pesticides with their biodegradable alternatives offers a way to decrease chemical residues. Pyrolysis liquids (PL) have been suggested as easily degradable and residue-free herbicides for agriculture. We tested the efficiency of PL (1%–10% of volume) containing peat mulch (PLM) in weed control under glasshouse and field conditions. We also estimated the length of the withdrawal period needed between PLM spreading and sowing/planting for crops and examined the light permeability and effects of PLM on soil temperature. In the glasshouse, the mulch amended with 5%–10% PL inhibited weed germination entirely. In the agricultural field, the number of weeds remained 44%–60% lower under PLM than under the control mulch. In a study performed in a city park, weed cover around the base of trees remained 64%–85% lower under PLM than without a mulch. However, a 7–21 d withdrawal period, depending on crop plant species, is needed to avoid injuring the crops. PLM inhibited sunlight effectively and the effects on soil heat sum across the growing season remained small. The weed-inhibiting effect of PLM is probably a result of both the PL compounds and the solid cover, formed by the sticky PL and peat fibres, which acts as a mechanical barrier. We conclude that the PLM is a promising alternative to plastic mulches.     

Insulinoma and Subclinical Peripheral Neuropathy in Two Dogs

Two dogs with diffuse, subclinical polyneuropathy associated with insulinoma are reported. Seizures were the dominant sign of central nervous system disease. One dog had clinical signs of facial nerve paralysis. Lesions in selected appendicular and cranial nerves included a mixture of demyelination, remyelination, and axonal degeneration. The incidence (range: 18-47%) of these changes far exceeded that of comparable nerves from six control dogs (range 0-11%). Myopathic and electrodiagnostic findings were compatible with the nerve changes.     

Non-dexamethasone-suppressible, pituitary-dependent hyperadrenocorticism in a dog

A 5-year-old female dog with hyperadrenocorticism was determined to have pituitary-dependent hyperadrenocorticism even though plasma cortisol concentrations were not suppressed after high-dosage dexamethasone administration. The diagnosis was based on a supranormal response of plasma cortisol to ACTH administration and a lack of suppression of plasma cortisol concentration after administration of 0.1 mg of dexamethasone/kg. Although a higher dosage of dexamethasone (1 mg/kg) did not cause suppression of plasma cortisol, plasma ACTH concentrations in the dog were increased above those in clinically normal dogs, supporting a diagnosis of pituitary-dependent hyperadrenocorticism. During treatment with mitotane, the dog became unconscious and died. Necropsy revealed a pituitary tumor that had compressed and displaced the hypothalamus. Although high-dosage dexamethasone suppression tests often are useful in the differential diagnosis of hyperadrenocorticism, a lack of suppression of plasma cortisol does not necessarily exclude pituitary-dependent hyperadrenocorticism.     

Measurement of total thyroxine concentration in serum from dogs and cats by use of various methods

OBJECTIVE: To compare results obtained from assay of total thyroxine (T4) concentration in serum of dogs and cats by use of 4 methods. SAMPLE POPULATION: Serum samples obtained from 98 dogs and 100 cats and submitted by veterinarians to an endocrine testing laboratory. PROCEDURE: Total T4 concentration was determined in each sample by use of 4 assay methods. Assay methods included a radioimmunoassay (RIA) marketed for use in dogs, an RIA for use in humans, a chemiluminescent enzyme immunoassay for use in humans, and an in-house ELISA. RESULTS: Total T4 concentrations obtained by use of all methods were significantly correlated. Bias-plot comparison revealed similar good overall agreement. Total T4 concentrations determined by use of the RIA marketed for use in dogs were generally lower than concentrations measured by use of the other methods. Clinical comparisons were made by evaluation of the T4 results in the context of the reference range recommended by each laboratory. A difference was found for clinical comparisons on the basis of T4 assay method when used to identify dogs as possible hypothyroid suspects. This difference was related more to the reference range used than to the absolute T4 value. The number of hyperthyroid-suspect cats with T4 values greater than the reference range was the same for each of the 4 assay methods. CONCLUSIONS AND CLINICAL RELEVANCE: Total T4 concentrations determined in dogs and cats by use of 4 commonly used methods provided similar and consistent results.