Thyroid dysfunction and iodine deficiency in a miniature jenny associated with neonatal congenital hypothyroidism dysmaturity syndrome

Abstract

A 7-year-old miniature donkey jenny with a history of stillborn foals in 2012 and 2013 delivered a miniature jack foal with congenital hypothyroidism dysmaturity syndrome in 2014. Thyroid dysfunction in the jenny was suspected, therefore, a thyrotropin releasing hormone stimulation test and mineral panel assessment were performed, which revealed an inadequate tetraiodothyronine response (10 nmol/l; reference range: 19.8 - 48.3 nmol/l) with low serum iodine (0.009 ppm; reference range: 0.02 - 0.049 ppm) and hair selenium concentration (0.42 ppm; reference range: 1.0 - 3.0 ppm). These findings were compatible with primary hypothyroidism due to iodine deficiency. The jenny was grazed on a pasture containing mustard plants (flixweed: Descurainia sophia; stinkweed: Thlaspi arvense; and wild mustard: Brassica keber1), which contain glucosinolates; their major metabolites can interfere with iodine uptake or organification, causing thyroid dysfunction. The jenny’s hypothyroidism and iodine deficiency were identified as the underlying cause of congenital hypothyroidism dysmaturity syndrome in the miniature jack foal.