Defects In Smell and Taste With Hypothyroidism

If you have a condition like hypothyroidism, your doctor will likely prescribe a thyroid hormone synthroid considerations replacement medication to help boost thyroid hormone levels in your body. Taste comes from both our taste buds and olfactory glands detecting chemicals in foods. The messages sent to your brain about both taste and smell travel alongsimilar signaling pathways.

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The subjective Ellsberg method modified by Pruszewicz was used primarily for selection of the control group and to obtain preliminary information on the state of the organ of smell in the other participants of the experiment. Thresholds of perception for those with a normal sense of smell determined by Pruszewicz for both oils of mint and anise are 12 mL. It is the volume of the saturated vapors of these oils at room temperature about (22 ± 1)°C administered with a syringe in about 0.5 sec into each nostril separately. Identical quality and the production of these oils according to the manufacturer—The National Chemical Reagents POCh—are guaranteed for 50 years 9, 15. In the control group the scope of the thresholds of perception for both anise and mint oils ranged in 3–8 mL. Świdziński was used with similar stimulus lasting for 0.5 s with speed of 10–30 mL/s.

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.

However total receptor count and density, olfactory epithelium surface area and thickness were found not to differ in relation to exposition with PTU. Twenty eight subclinical hypothyroid patients, and 31, age, gender, education level matched participants enrolled in the study. The control group was selected on the basis of the biochemical evidence of a normal thyroid function (TSH and fT3/fT4). The conversion rate to overt hypothyroidism was found between 2% and 6% in subclinical hypothyroid patients. Higher TSH levels or presence of anti-thyroid peroxidase antibodies (Anti-TPO) increase the conversion risk 1.

Defects In Smell and Taste With Hypothyroidism

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.

Statistical Analysis

Subclinical hypothyroidism has been accused for coronary heart disease, atherosclerosis, lipid metabolism disorders, neuropsychiatric disorders, infertility or pregnancy related problems with various strength of evidence 2,5. 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. To date, no studies have been undertaken to analyze latencies of olfactory responses recorded from nerves I and V in hypothyroidism in both subclinical and overt forms. Results of the correlation between TSH and latency of smell cortex evoked potentials PN5 at mint oil stimulation. Results of the correlation between TSH and latency of smell cortex evoked potentials PN1 at anise oil stimulation.

• Studies were included if they specifically focused on hypothyroidism and one of the five listed senses.
• Identical quality and the production of these oils according to the manufacturer—The National Chemical Reagents POCh—are guaranteed for 50 years 9, 15.
• 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.
• Animal studies revealed global affection of brain from hypothyroidism in terms of weight loss and cognitive decline.
• 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.
• One of the most common thyroid conditions is hypothyroidism, where your thyroid cannot produce a sufficient amount of thyroid hormone.

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• Situations like recent levothyroxine adjustment which did not reach the steady state, recovery phase of severe illnesses, thyroiditis by different etiologies, external sources of TSH variance, presence of biochemically TSH mimicking markers were excluded from this definition 2.
• The growing trend (visible in Figures 3–5) between TSH and latencies for the analyzed potentials proves to be a statistically significant relationship for PN1 at mint and anise stimulation (Figures 3 and 4) as well as for PN5 at mint stimulation (Figure 5).
• The most common cause of hypothyroidism is an autoimmune disease called Hashimoto’s thyroiditis, where chronic inflammation makes the thyroid unable to produce thyroid hormones.
• Sometimes, people experience pain on their tongue or other unusual symptoms when eating, like changes in food textures and temperature.
• Older people who take more drugs are at highest risk for changes in taste or smell because they take more types of drugs, and drugs may interact with each other to cause these changes.

We also presented here the value of the correlation coefficient rs-Spearman’s rank for significance of p. Changes in your ability to taste can vary from person to person, even in people with the same thyroid condition. When our bodies do not have enough thyroid hormone, it can lead to a general slowing of our body systems. A considerable difficulty seems to be how to ensure repeatable application of olfactory impulses.

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.

Making use of the impulse olfactometer with the electronically amplified olfactory stimulus (designed by Giesen and Mrowiński), Alber et al. (1972) made computerized averaging of 1.5- second electroencephalogram sections in responses to an olfactory stimulus 25. Then, Herberhold obtained cortex evoked olfactory potentials using 10–20 mL stimuli with 100–200 ms stimulation time. He obtained two separate potentials of 250 ms latency time for responses from the trigeminal nerve and 500 ms for those from the olfactory nerve 8.

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 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.