Voice dysfunction in hypothyroidism: An objective multidimensional acoustic study

ABSTRACT

Hypothyroidism [HT] is a well-recognized cause of voice disorders, although the mechanism is not fully understood. Much deeper understanding of the effect of hormones on the voice is imperative, so that enhanced management of the symptoms may be addressed. Acoustic analysis of voice can be informative because it affords quantitative analyses that carry potential for subsystem description and inference of the underlying mechanism of vocal breakdown. To date, available reports concerning objective analysis of voice characteristics in hypothyroidism are still lacking. This paper considers acoustic analysis of voice disorder in hypothyroidism to provide a quantitative description of voice characteristics that may contribute to our wider standing of the associated vocal deviations, and to assess the efficiency of computer-based acoustic waveform analysis in detecting such vocal dysfunction. Twenty-five patients with hypothyroidism were subjected to; auditory perceptual assessment using a modified GRBAS scale, videolaryngoscopy to exclude any laryngeal pathology, and acoustic voice analysis by Multi-Dimensional Voice Program [MDVP; Kay Elemetrics, NJ, USA]. These data were compared with age and sex matched 30 normal subjects. Dysphonia grade II, associated with increased roughness, breathiness, asthenic character, voice breaks, and reduced pitch are specific characteristics of the voice in hypothyroidism. In comparison to normal subjects, the F[o] related measures [F[o] F[o] standard deviation], perturbation measures [short and long term parameters], noise measures [harmonic to noise ratio] and voice irregularity measures [degree of unvoiced] showed statistically significant different values. The other acoustic parameters [soft phonation index, voice turbulence index and tremors measures], although showed a clinical difference, they did not reach level of significance. The perceptual and acoustic findings are indicative of laryngeal hypofunction in most patients with hypothyroidism. This incurred from a widespread influence of thyroid hormone deficiency on cortical motor and sensory processes which may result in changes of the motor and sensory control involved in the laryngeal phonatory mechanism. Moreover, good vocal production requires good physical condition and integrated control of physical and mental processes. Such processes are ultimately lost in hypothyroidism