Abstract
Thyroid hormone disorders are both congenital as well as acquired. According to a projection from several studies on thyroid diseases, it has been estimated that about 42 million people in India suffer from various kind of thyroid diseases (1) Thyroid hormone is closely associated with the development of the cognitive functions, thus deficiency of this hormone is said to have effect an overall impact on proper functioning of the body. The normal functioning of the thyroid gland and adequate levels in the blood are Needed for the formation and functioning of the middle ear, inner ear and the central auditory pathway. Thus, congenital hypothyroidism (CH) can be a potential risk factor for hearing impairment (2) if the hormones decrease or are absent during the development of the peripheral and central auditory system structures. This study was undertaken with the objective of studying the pattern of hearing loss in patients who have a deranged thyroid profile. The study was conducted among 50 patients who were known cases of thyroid disorder in the Otorhinolaryngology Department of our institute. The study was hospital based observational clinical study. The patients were subjected to thyroid profile test After this, those who satisfied the inclusion and exclusion criteria and were included, after detailed history and examination, patients were subjected to PTA, hearing loss was classified according to WHO guidelines. The age group of the patients was from 30-55 yrs. with the mean age being 42. On the basis of the t3, t4 and tsh levels, in the current study out of 50 patients,40 were hypothyroid (80%),with male to female ratio of 6:4. On pure tone audiometry, 15 patients had decreased hearing. The other 25 had normal hearing. The incidence of hearing loss in hypothyoroid patients in our study is 37.5%. On analaysis the PTA reports of these patients,9 patients (22.5%) had conductive hearing loss of mild variety, the mean value of hearing loss being 26.2 decibels. 2 (5%) patients had mixed variety of hearing loss, with sensorineural hearing loss at higher frequencies. All the remaining patients had sensorineural type of hearing loss, i.e., 10%. Of the 10 patients, that have hyperthyroidism 8 were female and 2 were male. 3 patients (30%) had hearing loss, all these 3 patients reported hearing losses at high frequencies and had moderate type of sensorineural hearing loss. Conclusion- From our current study, we could see that hearing loss is present in both extremes of thyroid hormone imbalance The dominant variety of hearing loss in thyroid disorder is sensorineural type, because thyroid hormone imbalance affects the inner ear function.
Keywords: Hypothyroidism, Hyperthyroidism, Hearing loss, Conductive deafness, SNHL
Introduction
Thyroid hormone disorders are both congenital as well as acquired. According to a projection from several studies on thyroid diseases, it has been estimated that about 42 million people in India suffer from various kind of thyroid diseases [1]
Thyroid hormone is closely associated with the development of the cognitive functions, thus deficiency of this hormone is said to have effect an overall impact on proper functioning of the body. The normal functioning of the thyroid gland and adequate levels in the blood are Needed for the formation and functioning of the middle ear, inner ear and the central auditory pathway. Thus, congenital hypothyroidism (CH) can be a potential risk factor for hearing impairment [2] if the hormones decrease or are absent during the development of the peripheral and central auditory system structures [3].It is known that in THYROID HORMONE IMBALANCE there is a reduction in cell energy production, compromising the microcirculation and, consequently the oxygenation and the metabolism of the involved organs. Inner ear structures, such as the stria vascularis and the Organ of Corti are also affected [4, 5]
Thyroid hormones control protein synthesis, the production of myelin and enzymes and the level of lipids in the central nervous system. Moreover, T4 also act as a neurotransmitter. Thus, it is believed that under hypothyroidism, hearing impairment can originate in the cochlea, in the central auditory pathways and/or in the retrocochlear region [6].
There is a relationship between hypothyroidism and hearing loss, the location of the affected part in ear has been subject to many new studies. Moreover, the occurrence of oedema of the Eustachian tube and middle ear mucosa and the possible ossicular chain dysfunction can predispose for CD in hypothyroid cases. [7]
The auditory system is highly sensitive to thyroid hormone disorders, Hearing loss is said to be associated with low t4 levels. Hence, hearing loss associated with tinnitus or vertigo.
Becomes the most common ENT presentation of congenital or acquired hypothyroidism.
In current study, we have evaluated the incidence of audiological derangement in newly diagnosed cases of thyroid hormone imbalance.
Material and Methods
The study was conducted among 50 patients who presented to us with symptoms of thyroid hormone imbalance at the otorhinolaryngology department of Mahatma Gandhi Hospital Jaipur.
The study was hospital based observational study.
The patients were then subjected to thyroid profile test. T3,T4 and TSH values were obtained and this was used to categorize the patients into hypothyroidism and hyperthyroidism.
After the diagnosis of the disorder, those who satisfied the inclusion and exclusion criteria and gave a consent to participate in the research were subjected to PTA.
All the patients were further referred to an endocrinologist for a detailed work-up and treatment.
Inclusion criteria
| Signs And Symptoms of Hypothyroidism (>; 3 months) | Signs And Symptoms of Hypothyroidism (>; 3 months) |
|---|---|
| weight gain | unintentional weight loss in spite of a normal or increased appetite, |
| breathlessness, palpitations, fatigue, slowed heart rate | rapid heartbeat (tachycardia),irregular heartbeat (arrhythmia),pounding of your heart (palpitations) |
| muscle weakness,muscle aches, tenderness and stiffness pain, stiffness or swelling in joints | fatigue, muscle weakness, nervousness, anxiety and irritability, tremor,sweating, difficulty sleeping, |
| dry skin,puffy face,thinning hair | skin thinning, fine, brittle hair |
| enlarged thyroid gland (goitre) | an enlarged thyroid gland (goitre) |
| heavier than normal or irregular menstrual periods | changes in menstrual patterns |
| increased sensitivity to cold, constipation | increased sensitivity to heat, more frequent bowel movements |
These patients were then subjected to thyroid profile and classified according to the below mentioned table.
Pure tone audiograms of all these patients were obtained.
Normal s.t3 = 0.97–1.69 ng/dl, s.t4 = 5.53–11 ng/dl, s. tsh = 0.465–4.68 ng/dl.
Exclusion criteria
Patients having congenital deafness, ear infections, congenital ear disease, ear trauma, other causes of sensorineural hearing loss or conductive hearing loss, patients on ototoxic drugs, patients with other endocrine and metabolic disorders were excluded from the current study.
*each patient was explained about the study, a written consent was obtained.
After which a detailed history was taken and patients were subjected to physical examination and thyroid profile test along with pure tone audiometry*
Pure tone audiograms recorded on ALPS (ADVANCED DIGITAL AUDIOMETER AD2100).
The frequencies tested were 250 Hz, 500 Hz, 1 kHz, 2 kHz, 4 kHz and 8 kHz. The average of the three frequencies i.e., 500 Hz, 1 kHz and 2 kHz were taken to be the pure tone average.
The hearing loss was then classified as per latest WHO guidelines.
| Hearing loss | Values in decibel |
|---|---|
| Normal hearing | 0-25 dB HL |
| Mild hearing loss | 26–40 dB HL |
| Moderate hearing loss | 41–55 dB HL |
| Moderate to severe hearing loss | 56–70 dB HL |
| Severe hearing loss | 71–90 dB HL |
| Profound hearing loss | > 90 dB HL |
Results
Out of the 50 patients who had participated in the study, 32 were female (64%) and 18 were male (34%).
The age group of the patients was from 30–55 yrs. with the mean age being 42.
On the basis of the t3, t4 and tsh levels, in the current study out of 50 patients,40 were hypothyroid (80%),with male to female ratio of 6:4.
On pure tone audiometry, 15 patients had decreased hearing. The other 25 had normal hearing.
The incidence of hearing loss in hypothyoroid patients in our study is 37.5%
On analaysis the PTA reports of these patients,9 patients (22.5%) had conductive hearing loss of mild variety, the mean value of hearing loss being 26.2 decibels.
2 (5%) patients had mixed variety of hearing loss, with sensorineural hearing loss at higher frequencies. All the remaining patients had sensorineural type of hearing loss, i.e., 10%
Of the 10 patients, that have hyperthyroidism 8 were female and 2 were male. patients (30%) had hearing loss, all these 3 patients reported hearing losses at high frequencies and had moderate type of sensorineural hearing loss.
Discussion
Most of the patients among the study population with hypothyroidism were females(60%), which was similar to other studies conducted by anand et al. and malik et al. [8]
According to study conducted by Anand et al. mean age of patients with hypothyroidism was 34.8 years (range; 15–50 years), comparable with mean age of patients with hearing loss in our study i.e. 42 years [8].
According to our study, the incidence of hearing loss in newly diagnosed cases of hypothyroidism is 37.5%, which is similar to a study conducted by Anil et al. in 30% hypothyroid patients had subjective hearing loss [9]. The medical literature quotes a hearing loss of 25% for patients with acquired hypothyroidism and 35%-50% for congenital hypothyroidism.
The incidence of conductive hearing loss, mixed hearing loss and SNHL amongst the hypothyroid cases of our study is 22.5%, 5% and 10% repectively.
This is in accordance with the study conducted by Dokianakis et al. [10] detected moderate SNHL in 8/23 and MD in 4/23 of them studied hypothyroid patients. Malik et al. [11] detected that 25% of patients had SNHL, 28.10% had MD, and 46.90% had CD. They advocated that subjective hearing loss in hypothyroid patients may be either due to actual conductive or SNHL.
Although there are various studies evaluating hypothyroid patients’ hearing, the studies conducted on hyperthyroid patients are limited [7, 12, 13].
In a study conducted by Karalı and Gü.lü[14] in 2009 on 25 hyperthyroid patients, the airway threshold values in the hyperthyroid group and the control group were compared audiometrically, and the airway thresholds of the hyperthyroid patients were found to be significantly higher at all frequencies (especially at 2000 Hz–8000 Hz), Similar results were seen in our study, hearing loss was found in 30% of patients with hyperthyroidism all at higher frequencies from 1 kHz-4 kHz.
Conclusions
From our current study, we could see that hearing loss is present in both extremes of thyroid hormone imbalance. It was found that hypothyroidism affects the ear at multiple sites producing various types of hearing impairment viz. conductive, sensorineural and mixed.Predominant variety of audiological impairment is that of sensorineural variety. The literature reviewed for the study showed that after subjecting the patients to thyroid hormone supplement therapy, the hearing may improve. The assessment of hearing levels in terms of early screening & follow up hence after should be done in patients with documented hormone level imbalance. Awareness about the same should be present on the side of medical professional as well as the patients.
Funding
No funding sources.
Declarations
Conflict of interest
None declared.
Ethical approval
The study was approved by the Institutional Ethics Committee.
Human animal rights
The research involved human participants, an informed consent was obtained from all participants before.enrolling them into the study
Informed consent
Due written consent was obtained from all the participants before enrolling them into the study, those who did not wish to consent were excluded from the study.
Footnotes
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Contributor Information
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