Equine thyroid dysfunction

Frank, Nicholas; Sojka, Janice E.; Messer, Nat T.

doi:10.1016/s0749-0739(02)00007-x

Cited by 30 publications

(58 citation statements)

References 31 publications

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“…There are no published reports of hypothyroidism resulting from iodine deficiency in adult horses, but it has been suggested that this differential should still be considered when goiter is detected. 2 Iodine deficiency would also be expected to increase the volume of the thyroid gland. Hashimoto's thyroiditislike disease has been reported as a post-mortem finding in horses in Eastern Europe.…”

Section: Resultsmentioning

confidence: 99%

Quantitative Pertechnetate Thyroid Scintigraphy and the Ultrasonographic Appearance of the Thyroid Gland in Clinically Normal Horses

Davies

Barber

Crisman³

et al. 2010

Veterinary Radiology &Amp; Ultrasound

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Abstract:The purpose of this study was to report the scintigraphic and sonographic appearance of the thyroid gland in clinically normal horses so these modalities could be used to assess the thyroid gland in this species. Horses were divided into two age groups. Group A consisted of 8 horses between 3 and 10 years of age and Group B of 7 horses between 11 and 20 years of age. Total T 4 concentrations were within the laboratory reference interval. Thyroid to salivary (T/S) ratio, percent dose uptake of pertechnetate and thyroid lobe volume were calculated. Echogenicity of thyroid lobes and presence of nodules were documented. The two groups were compared using appropriate parametric and nonparametic tests. Total T 4 concentrations were significantly lower in the older group. Sixty minute mean ± standard deviation (SD) T/S ratios for older versus younger horses were 5.8 ± 3.0 and 5.3 ± 2.2, respectively. Sixty minute median and interquartile ranges for percent dose uptake of pertechnetate for older versus younger horses were 3.64% (1.5 to 3.98%) and 2.55% (2.33 to 2.90%), respectively. Mean ± SD thyroid lobe volumes for older versus younger horses were 18.93 ± 5.16 cm 3 and 13.55 ± 3.56 cm 3 , respectively. Most thyroid lobes were hyper or isoechoic to the sternocephalicus muscle. Prevalence of thyroid nodules did not differ between groups. Older horses had trends for greater T/S ratios, percent dose uptakes and thyroid lobe volumes but had lower total T 4 concentrations. Further studies using scintigraphy and ultrasound in horses with thyroid disease are planned.

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Section: Resultsmentioning

confidence: 99%

Quantitative Pertechnetate Thyroid Scintigraphy and the Ultrasonographic Appearance of the Thyroid Gland in Clinically Normal Horses

Davies

Barber

Crisman³

et al. 2010

Veterinary Radiology &Amp; Ultrasound

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“…The effects of iodine deficiency in thyroid disorders, especially in endemic goitre areas, have been reported both in humans (Squatrito et al, 1981;Vigneri, 1988;Vermiglio et al, 1990;Vermiglio et al, 1995) and in different animal species (Hetzel and Mano, 1989;Maberly, 1994;Pugliese et al, 2007). Although diagnosis of thyroid disease in the horse is difficult (Frank et al, 2002;Messer and Johnson, 2007), cases of hypo- (Sojka, 1995;Breuhaus, 2002) and hyperthyroidism (Ramirez et al, 1998;Tan et al, 2008) in adult horses have been documented only rarely. Single measurements of T 4 and T 3 are difficult to interpret, particularly because thyroid hormone metabolism or transport can be affected by physiological or pathological states and by a variety of drugs (Breuhaus, 2002) as well as by the influence of circadian rhythm (Duckett et al, 1989;Komosa et al, 1990).…”

Section: Introductionmentioning

confidence: 99%

Influence of endemic goitre areas on thyroid hormones in horses

Medica

Fazio

Cravana

et al. 2011

Animal

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The aim of this study was to investigate thyroid hormone levels in horses stabled in two different locations on the island of Sicily. The study was carried out on a total of 72 clinically healthy Sanfratellano horses ranging in age from 5 to 9 years and weighing 585 6 40 kg. The results showed higher thyroxine values (P , 0.02) in horses stabled in an endemic goitre area (group II) than those observed in horses in a non-endemic area (group I). Unexpectedly, the T 4 /T 3 and the fT 4 /fT 3 rations were both lower in group I than in group II. The percentages of fT 4 to T 4 and of fT 3 to T 3 were both higher in group I than the percentages for group II. On the basis of gender, comparison between the two groups showed higher T 4 (P , 0.01) and fT 4 levels (P , 0.001) in males, and lower fT 3 (P , 0.001) and fT 4 levels (P , 0.005) in females stabled in the goitre endemic area. On the basis of age, younger horses (,7 years old) showed the highest thyroid hormone levels in both groups. Results suggest a physiological adaptive response of the equine species to an endemic goitre environment. The possibility that hypothyroidism is present in these horses is thus excluded and is supported not only by the lack of clinical signs, but also by the rarity of cases previously reported.

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“…23 An increase in serum rT 3 concentrations likely resulted from L-T 4 being con-verted to both T 3 and rT 3 . 1,26 At the beginning of the study reported here, horses of both groups had the expected increase in tT 3 concentration by 2 hours, but tT 4 concentrations were lower than anticipated. Lower concentrations of rT 3 have been associated with propylthiouracil-induced hypothyroidism in horses and are attributed to reduced production of T 4 by the compromised thyroid gland.…”

Section: Discussionmentioning

confidence: 59%

“…1 Despite the popularity for the use of L-T 4 in horses, little information is available to guide clinicians in selection of dosage or monitoring requirements. 1 Despite the popularity for the use of L-T 4 in horses, little information is available to guide clinicians in selection of dosage or monitoring requirements.…”

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confidence: 99%