**Dissolution Testing of Single- and Dual-Component Thyroid Hormone Supplements**

#### **Samantha L. Bowerbank, Michelle G. Carlin and John R. Dean \***

Department of Applied Sciences, Northumbria University, Ellison Building, Newcastle upon Tyne NE1 8ST, UK; samantha.bowerbank@northumbria.ac.uk (S.L.B.); m.carlin@northumbria.ac.uk (M.G.C.)

**\*** Correspondence: John.Dean@northumbria.ac.uk; Tel.: +44-191-227-3047

Received: 27 November 2018; Accepted: 6 March 2019; Published: 26 March 2019

**Abstract:** A method for the analysis of thyroid hormones by liquid chromatography-mass spectrometry was used for the dissolution testing of single- and dual-component thyroid hormone supplements via a two-stage biorelevant dissolution procedure. The biorelevant media consisted of fasted-state simulated gastric fluid and fasted state simulated intestinal fluid at 37 ◦C, and was investigated using an internationally recognized protocol. The dissolution profiles showed consistent solubilization for both single- and dual-component batches at pH 6.5 in the fasted-state simulated intestinal fluid.

**Keywords:** thyroid; dissolution; liquid chromatography-mass spectrometry
