Hypothyroidism is associated with prolonged COVID-19-induced anosmia: a case-control study

All the subjects underwent subjective threshold tests of smell perception determined by Ellsberg’s olfactory test modified by Pruszewicz and olfactory objective tests recording latency times of responses from cranial nerves I and V using two smells of mint and anise. In the study by McConnell 12 et al. smell and taste function was tested in 18 overt hypothyroid patients before and after treatment. Smell and taste tests were made with interrogation with the patients and similar testing methods which we have used. This study indicates that taste and smell deficits are common in hypothyroid patients and these deficits could be reversed with treatment. Fikentscher, who had used the olfactory method according to Ellsberg, obtained clear cortex responses with latency time 500–1000 ms 24.

Most importantly, these deficits can be remedied on average within 3 months with adequate treatment. Graphs in Figures 1 and 2 present a comparison of mean values, ranges, and standard deviations of PN1 and PN5 potentials in the subclinical and overt clinical hypothyroid groups as well as in controls. The apparatus for recordings of ERP (evoked reaction potentials) as well as the authors’ self-designed device that enables appropriate dispensing of olfactory stimuli were used 15. The modified self-designed device for objective measurement of cortex reaction potentials evoked by olfactory stimuli, which proves to be a unique investigation, is at present routinely used in our center in diagnostics and clinical evaluation of the organ of smell. Disturbances in perception thresholds of the olfactory test within the subjective scale were evaluated using Ellsberg’s olfactory method modified by Pruszewicz 13, 17. The method is however subjective, depending on individual perception of the patient.

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This study indicates that taste and smell defects are common clinical abnormalities in primary hypothyroidism, and suggests that these defects may contribute to the anorexia and lack of interest in eating which are frequently observed. The present studies revealed that patients with hypothyroidism score lower on olfactory tests and tests for bitter sensitivity compared to healthy controls, and that olfactory function and bitter sensitivity increase following 3 months of treatment with thyroid hormones. Importantly, the present study focused on patients with subclinical hypothyroidism whereas previous studies looked at clinically manifest hypothyrodism only. Results of the objective olfactory tests in hypothyroid patients (both forms of hypothyroidism) were compared to the results obtained from healthy subjects from the reference group.

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Studies were excluded if they synthroid gallstones were outside this paper’s scope or older than 2012. Studies were included if they specifically focused on hypothyroidism and one of the five listed senses. Patients with hypothyroidism had a significantly increased risk of sensorineural hearing loss, decreased perception of the blue-yellow color axis, decreased sense of olfaction and number of olfactory bulbs, and decreased thermogenesis. Hypothyroidism was also found to show increased length of COVID-19-induced anosmia and decreased bitter taste perception. It can be concluded that hypothyroidism has many effects on the senses, particularly an increased risk of sensorineural hearing loss.

Analysis of the correlation between TSH values and latencies of smell cortex evoked responses to olfactory and trigeminal nerves stimulation indicated that the greater the TSH value, the longer the latency of the recorded potential. Mean values, ranges, and standard deviations of recorded latency times of olfactory potentials PN1 and PN5 for all the groups of the subjects in stimulation with concentrated vapors of mint and anise oils. Currently there is insufficient knowledge about olfaction and taste functions in subclinical hypothyroidism, which represents a specific subgroup of hypothyroidism. Aim of the present study was to investigate the degree of smell and taste dysfunction in this group compared to healthy controls. Hypothyroidism has been found to have long-term effects on each of the senses, but with proper treatment, many of them can be significantly minimized. This paper analyzes the research on the impact of hypothyroidism on the senses of smell, taste, hearing, vision, and thermoregulation.

• Taste and smell functions were measured in 18 unselected patients with untreated primary hypothyroidism, and in 15 of the 18 patients after treatment with thyroid hormones.
• All subjects gave written informed consent and the institutional ethical committee approved the study protocol.
• Accordingly, we also looked for a similar relation between olfaction and thyroid function tests in subclinical hypothyroid patients but did not find a positive correlations.
• Subclinical hypothyroidism is defined as a situation in which serum levels of free thyroxin (fT4) are normal and serum thyroid-stimulating hormone (TSH) levels are elevated 1.

Accordingly, we also looked for a similar relation between olfaction and thyroid function tests in subclinical hypothyroid patients but did not find a positive correlations. Regarding changed fT3 levels in the normal interval of our results, expected correlation wouldn’t be occured. Apart from an effect on subjective perception of fragrances, a symptom of olfactory disorders proves to be a change in parameters of objective ERP recording of smell cortex potentials such as latency time or response amplitude.

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Implementing this method in diseases of the upper respiratory tract as a complementary method, for instance, in injuries of the craniofacial skeleton and surgical operations of the nasopharyngeal tumors, has already become quite common 5–7, 26, 27. Statistical analyses were performed using SPSS software version 15 (SPSS Inc. Chicago, IL, USA). The variables were investigated using descriptive (histograms, probability plots) and analytical methods (Kolmogorov—Smirnov test) to determine whether or not they were normally distributed. Descriptive analyses were presented as means ± standard deviations for normally distributed variables. For non-normally distributed/ordinal variables descriptive statistics are presented with number of cases with percentage, medians and interquartile range (IQR). Differences between numeric variables of two groups were tested with independent samples Student’s t-test for continuous variables displaying normal distribution and Mann—Whitney U test for continuous variables not displaying normal distribution.

Hypothyroidism is associated with prolonged COVID-19-induced anosmia: a case-control study

In this paper we show for the first time that the greater the TSH values, the longer the latency of smell cortex potentials recorded from both the trigeminal nerve N5 and the olfactory nerve N1. It is still controversial which mechanisms are playing a role for taste and smell loss in hypothyroidism patients. Different studies revealed that hypothyroidism has effects at multiple points of the gustatory and olfactory perceptual pathways.

Below are examples of commonly used drugs that may cause a change in your taste or smell. Julia Walker, RN, BSN, is a clinical nurse specializing in helping patients with thyroid disorders. She holds a Bachelor of Science in Nursing from Regis University in Denver and a Bachelor of Arts in the History of Medicine from the University of Colorado-Boulder.

• There seems to be no immediate link between subjective perception of fragrance and the delay of recorded smell cortex potentials in different forms of hypothyroidism.
• Your brain uses messages from both your tastebuds and your olfactory glands to determine your perceptions of smell and taste.
• The symptoms of a nervous system disorder, most frequently in the form of peripheral neuropathy, do not manifest themselves in a way that significantly impairs the patient’s ability.
• Our taste and smell sensations have their own receptor organs, but they are closely connected.
• Regarding changed fT3 levels in the normal interval of our results, expected correlation wouldn’t be occured.

It was possible to differentiate responses to stimuli irritating nerve V endings (potential PN5 within latency range 200–410 ms) as well as nerve I endings (potential PN1 within latency range 460–700 ms). The Kruskal-Wallis, Mann-Whitney’s significant differences tests, descriptive statistical tests, and Spearman’s rank correlation tests were used. In the subjective olfactory tests performed using Ellsberg’s olfactory test method modified by Pruszewicz in the hypothyroid patients, the smell perception thresholds (mint and anise) were normal in 85% cases. Definition of subclinical hypothyroidism requires normal levels of T3/T4 and increased TSH. Treatment of subclinical hypothyroidism doesn’t change levels of free T3 and T4 levels, reduces TSH levels to normal interval. Günbey et al. 19 investigated olfactory function in primary hypothyroid patients and found significantly lower scores in the hypothyroid group and a positive correlation between all threshold, discrimination and identification scores and free T3 levels.