Dataset Information

Effect of thyrotropin-releasing hormone stimulation testing on the oral sugar test in horses when performed as a combined protocol.

ABSTRACT:

Background

The use of parallel dynamic tests to identify insulin dysregulation (ID) and pituitary pars intermedia dysfunction (PPID) in horses could have better diagnostic utility than measuring baseline hormone concentrations, if the tests do not alter diagnostic interpretation of one another.

Hypothesis

Performing a thyrotropin-releasing hormone (TRH) stimulation test before an oral sugar test (OST) would not affect results of OST.

Animals

Twenty-six healthy university-owned horses.

Methods

A prospective randomized placebo-controlled, crossover design was used to evaluate 3 OST protocols: OST alone, TRH followed by OST (TRH?+?OST), and placebo followed by OST (placebo?+?OST). Agreement for plasma insulin concentrations and diagnostic interpretation were assessed with Bland-Altman and logistic regression analyses, respectively.

Results

Bland-Altman analysis of TRH?+?OST versus OST alone showed good agreement between testing protocols, with bias ± SD for insulin concentrations at baseline 0.4?±?4.7 ?IU/mL (95% limits of agreement [LOA], -8.8 to 9.7), 60?minute -0.5?±?22.6 ?IU/mL (95% LOA, -44.7 to 43.8), and 90?minute 1.9?±?20.6 ?IU/mL (95% LOA, -38.5 to 42.4) after OST, similar to placebo?+?OST versus OST alone. Diagnostic interpretation (positive/negative) was not different between protocols (TRH?+?OST versus OST alone [P = .78], placebo?+?OST versus OST alone [P = .77], or TRH?+?OST versus placebo?+?OST [P = .57]).

Conclusions and clinical importance

Concurrent testing for PPID and ID with a TRH stimulation test before an OST is an acceptable diagnostic tool for investigation of endocrinopathies in horses and allows accurate testing to be performed efficiently in 1 visit.

SUBMITTER: Hodge E

PROVIDER: S-EPMC6766522 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Effect of thyrotropin-releasing hormone stimulation testing on the oral sugar test in horses when performed as a combined protocol.

Hodge Elizabeth E Kowalski Alycia A Torcivia Catherine C Lindborg Sue S Stefanovski Darko D Hart Kelsey K Frank Nicholas N van Eps Andrew A

Journal of veterinary internal medicine 20190820 5

<h4>Background</h4>The use of parallel dynamic tests to identify insulin dysregulation (ID) and pituitary pars intermedia dysfunction (PPID) in horses could have better diagnostic utility than measuring baseline hormone concentrations, if the tests do not alter diagnostic interpretation of one another.<h4>Hypothesis</h4>Performing a thyrotropin-releasing hormone (TRH) stimulation test before an oral sugar test (OST) would not affect results of OST.<h4>Animals</h4>Twenty-six healthy university-ow ...[more]

PMID: 31432575

Similar Datasets

Project description:Thyrotropin releasing hormone (TRH: Glp-His-Pro-NH2) is a peptide mainly produced by brain neurons. In mammals, hypophysiotropic TRH neurons of the paraventricular nucleus of the hypothalamus integrate metabolic information and drive the secretion of thyrotropin from the anterior pituitary, and thus the activity of the thyroid axis. Other hypothalamic or extrahypothalamic TRH neurons have less understood functions although pharmacological studies have shown that TRH has multiple central effects, such as promoting arousal, anorexia and anxiolysis, as well as controlling gastric, cardiac and respiratory autonomic functions. Two G-protein-coupled TRH receptors (TRH-R1 and TRH-R2) transduce TRH effects in some mammals although humans lack TRH-R2. TRH effects are of short duration, in part because the peptide is hydrolyzed in blood and extracellular space by a M1 family metallopeptidase, the TRH-degrading ectoenzyme (TRH-DE), also called pyroglutamyl peptidase II. TRH-DE is enriched in various brain regions but is also expressed in peripheral tissues including the anterior pituitary and the liver, which secretes a soluble form into blood. Among the M1 metallopeptidases, TRH-DE is the only member with a very narrow specificity; its best characterized biological substrate is TRH, making it a target for the specific manipulation of TRH activity. Two other substrates of TRH-DE, Glp-Phe-Pro-NH2 and Glp-Tyr-Pro-NH2, are also present in many tissues. Analogs of TRH resistant to hydrolysis by TRH-DE have prolonged central efficiency. Structure-activity studies allowed the identification of residues critical for activity and specificity. Research with specific inhibitors has confirmed that TRH-DE controls TRH actions. TRH-DE expression by β2-tanycytes of the median eminence of the hypothalamus allows the control of TRH flux into the hypothalamus-pituitary portal vessels and may regulate serum thyrotropin secretion. In this review we describe the critical evidences that suggest that modification of TRH-DE activity in tanycytes, and/or in other brain regions, may generate beneficial consequences in some central and metabolic disorders and identify potential drawbacks and missing information needed to test these hypotheses.

Dataset Information

Effect of thyrotropin-releasing hormone stimulation testing on the oral sugar test in horses when performed as a combined protocol.

Background

Hypothesis

Animals

Methods

Results

Conclusions and clinical importance

Publications

Effect of thyrotropin-releasing hormone stimulation testing on the oral sugar test in horses when performed as a combined protocol.

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