EtiologyHypothyrodism is often associated with night blindness, due to the liver's inability to convert beta-carotene into vitamin A [Starr2005, pg 114].
References [Starr2005]  Mark Starr. Hypothyroidism Type 2: The Epidemic Columbia, MO: Mark Starr Trust (2005). Amazon Updated 2011 added: Hashimoto's & Grave's diseases.