Thyroid Function and Dysfunction in Term and Premature Equine Neonates

Abstract

BackgroundThis study was performed to compare thyroid function of premature foals to term foals.HypothesisPremature foals are more markedly hypothyroxinemic than expected for their severity of illness alone.AnimalsTwenty clinically normal term foals; 28 sick, hospitalized term foals; 24 sick, hospitalized premature foals.MethodsThyroid hormones (TH) and thyrotropin (TSH) were measured, both at rest and in response to thyrotropin‐releasing hormone (TRH), in the 3 groups of foals. Clinical and clinicopathologic data were recorded.ResultsNormal foals had high TH at birth, which decreased over the first month into the normal reference range for adult horses. TSH was within the normal adult reference range soon after birth, and did not change over time. At 24–36 hours of age, triiodothyronine (T3) was significantly lower in both premature and term hospitalized foals compared to normal foals; premature foals were not different from term hospitalized foals. Thyroxine (T4) was not different between normal and term hospitalized foals, but was significantly lower than in premature foals of both of these groups. TSH was not different among the 3 groups. TRH stimulation tests identified significant differences in T4 among all 3 groups of foals, whereas T3 was similar in premature and term hospitalized foals and different from normal foals. TSH response to TRH was significantly higher in premature foals compared to normal foals.Conclusions and Clinical ImportanceThe hypothalamic‐pituitary‐thyroid axis is different in foals compared to adult horses. Sick foals exhibit nonthyroidal illness syndrome. Premature foals are more markedly hypothyroxinemic than can be accounted for by their severity of illness alone.

Serum cortisol and thyroid hormone concentrations and survival in foals born from mares with experimentally induced ascending placentitis

“…Similar results were found in another study with foals affected with perinatal asphyxia syndrome in which TH concentrations were not associated with survival 16 . Other foal studies have found association between low TH concentrations and death 14,17 . In a study in which a single blood sample was collected to assess TH concentration in foals that were between 1 and 192 hours old, septic nonsurviving foals had lower levels of T 3 , F T 3 , and F T 4 than septic surviving foals 14 .…”

“…Other study that evaluated TH levels in foals that were 24 to 36 hours old demonstrated that sick nonsurviving foals had decreased levels of F T 3 and premature nonsurviving foals had decreased levels of F T 3 and F T 4. 17 However, in the foals of our study, TH concentrations were measured multiple times over a 1‐week period since the physiological decrease in TH concentrations in newborn foals suggests that for proper TH result interpretation, they should be compared to age‐matched healthy foals.…”

“…There are few publications on NTIS in neonatal foals 14‐17 . Furthermore, the information available is generally from hospital admissions, making it difficult to compare TH concentrations in sick and healthy age‐matched foals.…”

Kongenitale Struma beim neonatalen Fohlen

“…Da die Schilddrüsenhormone an der Ausbildung des Skelettund Nervensystems beim Fetus beteiligt sind (3,5,11,20,23), spiegeln sich die Folgeerkrankungen entsprechend im Organismus wider. Folgende Symptome wurden beschrieben: Strecksehnenruptur an den Vordergliedmaßen (1,2,16,19,20), unreife Tarsal-und Karpalknochen mit verspäteter Ossifikation (1,2,15,16,19,20,28), Beugefehlstellung der Vorderextremitäten (1,2,16,19,20), Achsenfehlstellung der distalen Vordergliedmaße (2) und Brachygnathia superior (1,2,16,19,20).…”

“…Auch Schusser et al (24) berichteten von diesem Krankheitskomplex in Verbindung mit lebensschwachen Fohlen. Ferner wurde ein kongenitaler Hypothyreoidismus mit dem neonatalen Atemnotsyndrom (22,23) und dem Auftreten einer Prä-oder Dysmaturität (1,3) in Verbindung gebracht. Als Ursache der kongenitalen Struma wird eine inadäquate Jodversorgung der Stuten während der Gravidität angesehen (1,2,8,9,10,12,15,16,19,25,26).…”