What medications can affect your taste or smell?

The studies by Mackay-Sim and Beard conducted on mice indicate that thyroxine is necessary for normal development of the nervous system, including the genesis of new olfactory receptor neurons 4, 5. Although hypothyroidism disrupts development of the olfactory epithelium, it does not cause however complete atrophy of neurons 6. Olfactory disorders are most frequently caused by conduction disorders of the sensory stimulus mainly due to upper respiratory tract infections, infections of the nose and sinuses, and injuries or as an idiopathic excessive synthroid disorder 7–9. 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.

Hypothyroidism Affects Olfactory Evoked Potentials

• If you have changes in smell or taste that make it hard for you to take a drug, do not stop on your own.
• Results of the correlation between TSH and latency of smell cortex evoked potentials PN1 at anise oil stimulation.
• Correlation analysis were made with Pearson’s and Spearman’s correlation analyses, respectively.
• If you suspect your thyroid may be the cause, start by getting your thyroid checked.
• Studies were excluded if they were outside this paper’s scope or older than 2012.

This is all more understandable that in the majority of respondents olfactory functions on discrete scents of mint and anise were not disturbed, though we found also in all this cases delayed latencies of cortical potentials PN1  and  PN5. However, differences were noticed in the objective tests in which evaluation concerned recordings of electric responses to olfactory stimulation of nerves N1 and N5 by means of aromatic smells, mint and anise in groups of healthy subjects and hypothyroidism. The ERA 2250 apparatus by Madsen Electronics is used to record evoked responses by means of Beckman electrodes placed to the forehead and bilaterally to the nape (or the neck). The technique of summing and averaging responses to a quantitatively identical stimulus was used. Anise oil stimulated endings of the olfactory nerve and mint oil endings of the olfactory and trigeminal nerves.

• Study designed in prospective cross-sectional fashion and approved by the Clinical Research Ethics Committee of Haydarpasa Training Hospital (HNEAH-KAEK 2013/ KK/117).
• Despite its small size, the thyroid plays a significant role in how your body functions.
• The Kruskal-Wallis, Mann-Whitney’s significant differences tests, descriptive statistical tests, and Spearman’s rank correlation tests were used.
• Likely, your ability to taste your food is also reduced until your nasal congestion resolves.
• 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.

A subjective olfactory perception does not always correlate with objective tests of the central nervous system (CNS) responses 18. Bajaj 6 et al. was searched for cognitive functions in subclinical hypothyroid patients. This study revealed that increasing levels of TSH correlate with the decline in cognitive functions. Animal studies revealed global affection of brain from hypothyroidism in terms of weight loss and cognitive decline.

Orthonasal Olfactory Testing

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.

Correlation analysis were made with Pearson’s and Spearman’s correlation analyses, respectively. Some people also attribute changes in taste to the medication used to treat thyroid conditions, such as thyroid hormone replacement medications. For example, some reports indicate that it is not uncommon to have a metallic taste in your mouth if you take levothyroxine. However, one study found thataltered taste improved significantly in the study group after being on levothyroxine for three months. The fact is we don’t know exactly why an altered sense of taste can be a symptom of a thyroid issue. But, one more recent study of hypothyroidism shows evidence that low thyroid hormone can lead to burning mouth syndrome and an altered taste sensation.

According to a 2018 review in the World Journal of Otorhinolaryngology Head and Neck Surgery, studies and reviews show that more than 350 drugs can cause changes in taste, and more than 70 drugs can cause changes in smell. Our study included 31 controls and 28 untreated subclinical hypothyroid patients. Mean age was 29±8.5 years in the control group and 29.9±9.0 years in the study group. Groups did not differ significantly in terms of age, sex and education level (Table 1).

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.

Results of the correlation between TSH and latency of smell cortex evoked potentials PN1 at mint oil stimulation. Sensitivity for “bitter” was significantly decreased in hypothyroid patients compared to controls. Recent work by Clark et al. 18 indicated that tasting of bitter compounds would modulate thyrocyte function and T3/T4 production. Thus, the present findings could be the result of a complex network between taste and thyroid functions. Tests for smell, taste and endocrine function of patients and controls were recorded before and after treatment. Subclinical hypothyroid patients exhibited a significantly decreased olfactory sensitivity; in addition, bitter taste was significantly affected.

Table 2. Olfactory and Taste results of Patients (before and after treatment) and Controls.

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.

Prevalence of subclinical hypothyroidism is relatively high among elderly and women. Our taste and smell sensations have their own receptor organs, but they are closely connected. Likely, your ability to taste your food is also reduced until your nasal congestion resolves. When food doesn’t taste right, it can alter your appetite and change your eating habits.