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

Domestic Animal Endocrinology
M Diaz-EspineiraH S Kooistra

Abstract

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. Three of these dogs were followed up for another 1.5 years while receiving l-thyroxine. Adenohypophyseal function was investigated at 2-month intervals with the combined intravenous injection of CRH, GHRH, GnRH, and TRH, and measurement of the plasma concentrations of ACTH, GH, LH, PRL, and TSH. In addition, after 2 years of hypothyroidism a single TRH-stimulation test and a somatostatin test were performed, with measurements of the same pituitary hormones. Every 6 months the pituitary gland was visualized by computed tomography (CT). Induction of PH led to high plasma TSH concentrations for a few months, where after concentrations gradually declined to values no longer significantly different from pre-PH values. A blunted response to stimulation of TSH release preceded this decline. Basal plasma GH concentrations increased during PH and there was a paradoxical hyperresponsiveness to TRH stimulation. Basal GH concen...Continue Reading

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Citations

Apr 27, 2010·Journal of Feline Medicine and Surgery·Björn P MeijHans S Kooistra
May 5, 2011·New Zealand Veterinary Journal·C T Mooney
Jan 30, 2009·Journal of Veterinary Internal Medicine·M M Diaz-EspiñeiraH S Kooistra
Jun 9, 2012·Journal of Veterinary Internal Medicine·M CamposS Daminet
Dec 24, 2015·Journal of Veterinary Internal Medicine·Annemarie M W Y VoorbijHans S Kooistra
Jul 14, 2012·Journal of Comparative Pathology·B P MeijJ Ijzer
Aug 3, 2013·Veterinary Clinical Pathology·R LavouéC Trumel
Oct 8, 2014·Australian Veterinary Journal·T JohnstoneC T Mooney
Jul 6, 2014·The Veterinary Journal·F FracassiM Caldin
Jul 4, 2012·Virchows Archiv : an International Journal of Pathology·Mark E JentoftBernd W Scheithauer
Nov 28, 2017·Journal of Feline Medicine and Surgery·Daphné RochelLaetitia Jaillardon
Feb 24, 2021·Journal of Veterinary Internal Medicine·Kirsten L van BokhorstBjörn P Meij
Mar 2, 2021·The Veterinary Journal·K SandersB P Meij

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