Audiological Evaluation in Goitrous Hypotyhroidism

doi:10.4236/ijohns.2013.25042

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International Journal of Otolaryngology and Head & Neck Surgery, 2013, 2, 201-206

http://dx.doi.org/10.4236/ijohns.2013.25042 Published Online September 2013 (http://www.scirp.org/journal/ijohns)

Audiological Evaluation in Goitrous Hypotyhroidism

M. K. Aggarwal1, Gautam Bir Singh2*, Ranjan K. Nag1,

S. K. Singh1, Rajesh Kumar1, Mayank Yadav2

1Institute of Medical Sciences, BHU, Varanasi, India

2Lady Hardinge Medical College & Associated Hospitals, New Delhi, India

Email: [email protected]

Received May 26, 2013; revised June 25, 2013; accepted July 10, 2013

which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

ABSTRACT

Obje ctive: To determine the incidence of deafness in patients suffering from goiterous hypothyroidism exclusively and

to evaluate the role of L-thyroxine therapy in improving the hearing in this group of patients. Study Design: A prospec-

tive cohort study. Materials and Methods: Hearing status was evaluated in a sample size of 100 consecutive patients

reporting to the ENT/Endocrinology department of Institute of Medical Sciences, Banaras Hindu University, Varanasi,

UP with the diagnosis of goitrous hypothyroidism. The study group included patients in the age group of 5 to 65 years

belonging to either sex. Patients with detected hearing loss were categorized into group A, and all other patients were

designated group B. L-Thyroxine treatment for goitrous hypothyroidism was initiated in all the cases. At the end of 6

months, a repeat audiogram was done in all the patients in order to evaluate the efficacy of the said treatment protocol on

the hearing in these patients. The data were tabulated and statistically analysed using Paired Students “t” test. Results:

An overall 39% hearing loss was observed in patients with goitrous hypothyroidism. 15% cases had sensorineural hear-

ing loss, 13% had mixed hearing loss and 8% had a conductive hearing loss. A statistically significant hearing improve-

ment was recorded in this study by L-thyroxine treatment in group-A, and no deterioration of hearing was recorded in

group-B. Conclusions: The incidence of sensorineural hearing is less in patients with goitrous hypothyroidism (15%) as

compared with the overall incidence of sensorineural hearing loss reported for hypothyroidism (30% - 40%). Further,

there is a definitive improvement in hearing with the use of L-thyroxine treatment of goitrous hypothyroidism.

Keywords: Hypothyroidism; Goitre; Hearing Loss; L-Thyroxine Treatment

1. Introduction

Hearing loss was first reported in acquired hypothyroid-

ism in 1907 [1]. Over a period of time, a distinct associa-

tion between hypothyroidism and auditory system dys-

function has been reported in medical text [2], though

there are studies which have failed to elucidate a defini-

tive relationship between hypothyroidism and deafness

[3-5]. The medical literature now mentions vertigo, hear-

ing loss, tinnitus and pruritic external auditory canal as

important vestibular and audiological symptoms of hy-

vpothyroidism [2].

Hypothyroidism is associated with all types of deaf-

ness: sensorineural, mixed and conductive, however, the

real incidence and pathophysiology of this hearing loss in

these patients is still uncertain. This is attributed to the

marked paucity of literature on the cited subject. The in-

cidence of hearing loss varies from 25% to 50% with a

higher incidence in congenital hypothyroidism [6,7].

Moreover, the results of audiological evaluation of pa-

tients with hypothyroidism under treatment with L-Thy-

roxine [LT] are conflicting. There are studies which have

highlighted the importance of this modality of treatment

in improving hearing in hypothyroid patients [8-12], but

literature is also replete with studies which have found no

correlation between the two [3-5,13,14]. Considering this,

in order to broaden the studies in this line of research a

prospective study was initiated exclusively in goitrous

hypothyroid patients with the aim to:

1) Determine the incidence of hearing loss in these pa-

tients;

2) Evaluate the effect of LT therapy on this hearing

loss in these patients.

To our knowledge, the current study is unique, in that

audiological evaluation of goitrous hypothyroidism has

not been previously reported in medical literature.

*Corresponding author.

M. K. AGGARWAL ET AL.

202

2. Materials & Methods

A prospective outcome analysis study was carried out in

the departments of Otorhinolaryngology & Endocrinol-

ogy, Institute of Medical Sciences, Banaras Hindu Uni-

versity, Varanasi, UP, India from September 2002 to

September 2005. For the purpose of this study 100 con-

secutive patients of either sex suffering from goitre with

hypothyroidism were recruited in the study design. The

study was approved by the University Board of Studies

& Ethics committee, and an informed consent was man-

datory for recruitment in the study design. Paediatric pa-

tients were also recruited in the study design.

All the patients of goitre reporting either to the otorhi-

nolaryngology department or endocrinology department

were subjected to detailed history taking and clinical ex-

amination. A FNAC (fine needle aspiration cytology),

USG (ultrasound) of the enlarged thyroid and screening

for thyroid function was done in all the cases to confirm

the nature of the goitre and the hypothyroidism. The pa-

tients were specifically screened for thyroid dysfunction

by T4 and TSH levels. Thyroid function test were done

by RIA [Radio Immune Assay], the kit for which was

supplied by Bhabha Atomic Research Centre, Mumbai,

India. Only patients with proven hypothyroid status were

enrolled in the study:

● Serum thyroxine level (T4): normal range 4 to 13 mi-

crograms/dl;

● Serum thyrotropin (TSH): normal range 0.3 to 6 mi-

cro IU/ml.

Their particulars, detailed history of thyroid swelling

and disease along with clinical examination were entered

in a Performa. Tests to diagnose aetiology of hypothy-

roidism and goitre were also done. A special note of

deafness, vertigo, and tinnitus was also made. The pa-

tients of deafness were further evaluated by tuning fork

test and pure tone audiogram [PTA]. Alps advanced di-

agnostic audiometer AD100 with the following standards

was used for PTA testing:

● Tone audiometer: EN60645-1/ANSI S3.6, Type 2;

● Speech audiometer: EN60645-2/ANSI S3.6, Type B

or B-E.

It would be prudent to note that hypothyroid patients

with deafness due to any other causes like:

● Chronic suppurative otitis media;

● Meningitis;

● Head Injury;

● Presbyacusis (patients above 60 years were not re-

cruited in this study);

● Ototoxic drugs etc were excluded from the study de-

sign.

Finally, these patients with audiogram proven deafness

were categorized in a designated special group-A, all

other patients were enrolled in group-B. Patients in both

the groups continued to receive thyroxine treatment un-

der the supervision of endocrinology department and a

regular monthly follow-up was maintained. At the end of

6 months a repeat audiogram was done and the hearing

status was once again evaluated. A 10 db improvement in

two consecutive frequencies was regarded as an audi-

ological improvement [15,16]. The data was tabulated

and statistically analysed by paired students “t” test.

In this study patient with Hashimoto’s thyroiditis, io-

dine deficiency, thyroid malignancy, irradiated thyroid

malignancy, Pendred’s Syndrome and hyperthyroid pa-

tients treated with drugs/radioiodine etc were all included

in the study design. Distinguishing congenital hearing

loss due to “Pendred’s Syndrome” and other causes of

congenital hearing loss was difficult as “Perchlorate Test”

was not available in our institution. Thus all the cases of

congenital hearing loss with hypothyroidism and goitre

were clinically regarded as “Pendred Syndrome”. Al-

though we recruited cases with diagnosis of hypothy-

roidism with goitre which reported for the first time to

ENT/endocrinology department OPD of our institution,

however during the course of study it was revealed that

some of these patients had taken replacement in the past

for short duration. This was probably due to the rural

background, poor socio-economic status and illiteracy of

our patient profile.

3. Results

Out of a total of 100 patients with goitre and hypothy-

roidism, 70 were females and 30 were males. The age

group of patients ranged from 5 years to 64 years. There

were 12 paediatric patients. The age distribution of these

patients is given in Table 1.

A total of 39 patients had an audiological proven deaf-

ness. However over a period of time 3 patients were lost

in follow-up, thus for statistical interpretation and dis-

cussion in this study the results in 36 patients were taken

into consideration. Out of these 36 patients 8 patients had

conductive hearing loss, 15 patients had sensorineural

hearing loss and 13 patients had a mixed hearing loss.

The distribution of these cases in accordance with WHO

classification is shown in Table 2. The relationship of

this hearing loss with the levels of T4 is also given in

Table 2. The mean T4 levels which were associated with

normal hearing are 2.7 micrograms. From the table it is

clearly evident that the severity of the hearing loss is

directly proportional to the decreasing value of T4 levels.

The hearing thresholds were again measured 6 months

later in euthyroid state post thyroxine therapy. The Table

3 shows the audiological gains after L-thyroxine therapy

in each ear separately and the overall gain in all the 36

patients. The analysis of the data revealed:

1) The 10 db hearing improvement or more is seen in 9

M. K. AGGARWAL ET AL. 203

Table 1. Age distribution.

AGE GROUPS [Yrs]

No of

Pt’s 5 - 14 15 - 24 25 - 34 35 - 44 45 - 54 55 - 60Total

Group-A 3 7 10 12 6 1 39

Group-B 9 23 9 12 5 3 61

Total 12 30 19 24 11 4 100

*No of Pt’s: Number of patients; *Group-A: Goitrous hypothyroid patients

with hearing loss; *Group-B: Goitrous hypothyroid patients with normal

hearing.

Table 2. Hearing loss (with correlation to mean T4 levels).

Hearing Loss Number of Cases

[100]

Mean T4

(micrograms/dl)

Normal 61 2.7

Mild (25 - 40 db) 11 2.6

Moderate (41 - 55 db) 10 2.4

Moderately severe

(56 - 70 db) 14 2.3

Severe (71 - 90 db) 04 1.8

Profound (>90 db) nil N/A

Table 3. Overall response to l-thyroxine treatment.

Imp

[db] −7 −6 −5 −4 −3 −2 −1 0 1 23 4 5 6 7 8 9101112

No of

Ears 1 0 0 0 2 1 0 4 0 109 0 16 0 13 7 0702

No of

Pts 1 0 0 0 0 0 0 0 0 4 7 0 8 0 5 6 0401

*Imp (db): improvement in Pure tone audiometry [average] in decibels; *No

of ears: total number of ears i.e. 36 × 2 = 72; *No of pts: total number of

patients in study design = 36.

ears only;

2) The 10 db hearing improvement or more in totality

is seen only in 5 patients;

3) A decrease in hearing was recorded in 4 ears across

various frequencies;

4) One case recorded a significant decrease in hearing

by 7 db;

5) A hearing improvement was recorded in 64 ears,

ranging from 2 db to 12 db;

6) A hearing improvement was recorded in 35 of the

36 patients.

The Table 4 highlights the improvement in hearing

following thyroxine treatment in each specific frequency

i.e. 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz. The study

of the data indicates that:

1) A gain of 10db or more was recorded in 24, 31, 22,

and 25 ears at 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz

respectively;

Table 4. Response to l-thyroxine treatment (frequency spe-

cific/each ear).

Improvement in hearing (db) (36 × 2 = 72 ears)

Frequency

(Hz) −10 −5 0 5 10 15 Total

500 2 13 13 20 13 11 72

1000 0 08 16 17 16 15 72

2000 0 10 20 20 14 08 72

4000 0 07 18 22 14 11 72

2) Maximum significant gain of 10 db or more was

seen at 1000 Hz (31 ears);

3) A decrease in hearing threshold varying from −1 to

−10 db was seen maximally at 500 Hz (15 ears). Other

frequencies showed a miniscule upto −5 db decrease in

hearing only.

The overall audiological improvement after thyroxine

treatment was statistically analysed using paired students

“t” test by comparing the average hearing threshold by

pure tone audiometry for each patient at 500, 1000, 2000,

3000, 4000 Hz before and after thyroxine therapy (Table

5). In this study the value of “P” was found to be highly

significant (Table 5). Thus, indicating that thyroxine the-

rapy benefits hearing in goitrous hypothyroid patients. In

addition, it would be prudent to note that no significant

deterioration in hearing was detected in any patient of

group-B at the end of 6 months.

In this study 17 patients also had tinnitus. And a his-

tory of vertigo was recorded in 39 of the 100 patients.

4. Discussion

Goitre is defined as an enlargement of thyroid gland.

Worldwide about 90% of cases are due to iodine defi-

ciency. In countries that use iodized salt, Hashimoto’s

thyroiditis is the most common cause [17]. Further it is

important to note that over a period of time, patients of

goitre due to lack of iodine can develop hypothyroidism

[17]. Hence, the evaluation of hearing in goitrous hypo-

thyroidism assumes clinical importance.

In our study group of goitrous hypothyroid we found

that 39% of patients had some hearing loss. Out of these

15% cases had sensorineural hearing loss; a conductive

hearing loss was seen in only 8% cases, the remaining

13% recorded a mixed hearing loss. The medical litera-

ture quotes a hearing loss of 25% for patients with ac-

quired hypothyroidism and 35% - 50% for congenital

hypothyroidism [6,7]. Moreover an incidence of 30% -

40% for sensorineural hearing loss has been reported for

myxoedema in medical text [2]. From the above account

it is clearly evident that patients with goitrous hypothy-

roidism have a comparable hearing loss (39%), but the

incidence of sensorineural loss is less. Nevertheless, a

M. K. AGGARWAL ET AL.

204

Table 5. Statistical analyses of hearing improvement with

l-thyroxine treatment.

Average hearing threshold in db

(pure tone audiometry)

S. NO

(Patients with

deafness) Group-A1

(Pre treatment)

Group-A2

(Post treatment)

1. 71.33 68.33

2. 40 36.66

3. 30 28.33

4. 60 51.66

5. 53.33 45

6. 68.33 61.66

7. 35 31.66

8. 68.33 65

9. 70 60

10. 56.67 53.33

11. 46.67 36.66

12. 46.67 41.66

13. 45 43.33

14. 80 75

15. 78.33 73.33

16. 66.67 55

17. 41.66 36.66

18. 41.67 36.66

19. 41.67 38.33

20. 50 43.33

21. 85 80

22. 45 38.33

23. 48.33 38.33

24. 76.66 75

25. 38.33 36.66

26. 40 36.66

27. 55 46.66

28. 68.33 60

29. 60 55

30. 65 61.66

31. 61.67 53.33

32. 58.33 51.66

33. 30 36.66

34. 58.33 51.66

35. 65 56.66

36. 40 30

Statistical Calculations

Mean 55.2308 49.7183

Standard Deviation [SD] 14.7682 14.0448

Standard Error of mean [SEM] 2.4614 2.3408

*Confidence Interval: The mean group-A1 minus Group-A2 = 5.5125; 95%

confidence interval: 4.3466 to 6.6784; *Intermediate values used in calcu-

lations: t = 9.5986, df = 35, standard error of difference = 0.574; *P value

and statistical significance: Two tailed P value = <0.0001, which is ex-

tremely significant.

sensorineural element tends to predominate (28%) in

these cases of goitrous hypothyroidism too. Also most of

the patients had a moderate or moderately severe hearing

loss (Table 2).

In this study we recorded an overall statistically sig-

nificant hearing improvement after thyroxine treatment

(Table 5). But the author’s would like to highlight that a

significant 10 db improvement was observed in only 5

cases i.e. only about 13% cases had an objective audi-

ological improvement (Table 3), though many cases

claimed a subjective improvement in hearing. And one

case also had deterioration in hearing. Further it was ob-

served that the thyroxine treatment influences the hearing

maximally at 1000 Hz, the frequency at which 31 ears

had a significant gain of 10 db or more (Table 4). There

are diverse views regarding improvement in hearing in

hypothyroid patients with thyroxine treatment. Studies by

Vent Hoff W (1979) [9], Rubeinstein M et al. (1974)

[10], Howarth AF et al. (1956) [11] and Anand VT et al.

(1989) [12] have reported an improvement in hearing

following thyroxine therapy. On the other hand studies

by Post JT (1964) [13], DeVos JA (1963) [14], Parving

A et al. (1973) [3] and yet another study by Parving A et

al. (1983) [4] have not reported any significant im-

provement in hearing post treatment with thyroxine. A

recent study which analyses Meniere’s disease and thy-

roid dysfunction also found no statistically significant

difference between prevalence, pattern and severity of

hearing loss between patients of Meniere’s disease taking

thyroxine supplements and patients who were not [5].

The exact Pathophysiological changes leading to hear-

ing loss in hypothyroidism have not yet been unveiled. It

is believed that hypothyroidism leads to decrease in cell

energy production, compromising the microcirculation

and consequently the metabolism and oxygenation of the

involved organ. In the case of hearing loss this affects the

inner ear structures: stria vascularis and organ of corti

[18,19]. Thyroid hormone also controls protein synthesis,

myelin production and enzymes and the level of lipids in

the central nervous system. In addition, T4 also acts as a

neurotransmitter. Thus it is speculated that in hypothy-

roidism hearing impairment can originate in the cochlea,

central auditory pathway and/or in the retrocochlear re-

gion [20]. Moreover, in most of the studies brainstem

electric response does not show significant reversal fol-

lowing L-thyroxine therapy [4,12,14]. Thus it is widely

accepted that improvement in hearing following levothy-

roxine therapy is attributed to improved general condi-

tion of the patient resulting in improved co-operation in

psycho-acoustic testing, the so called functional improve-

ment in central deafness [4,12,14]. The histological ex-

amination of temporal bones in these patients has also

failed to show accumulations of glycoaminoglycans [4,

21,22]. It would however be imperative to note that con-

M. K. AGGARWAL ET AL. 205

ductive hearing loss in hypothyroidism is secondary to

Eustachian tube mucosal oedema [23].

Although it was not the endeavour of this study to

analyse the vestibular changes in goitrous hypothyroid-

ism, the authors would like to highlight that almost 39%

cases had a history of vertigo, out of which 26 patients

had an subjective improvement after levothyroxine ther-

apy at the end of 6 months. In this context it would be

important to note that the medical text mentions that al-

most 66% of patients of hypothyroidism suffer from ver-

tigo [2]. Tinnitus too was present in 17 cases. Nine of

these cases recorded a subjective improvement in form of

decrease in the duration and intensity of the tinnitus.

Thus a joint involvement of cochlear and vestibular sys-

tem is also seen in goitrous hypothyroidism as has been

reported for other metabolic disorders [24]. The authors

would also like to highlight that no case of Meniere’s

disease i.e. the classical triad of vertigo, deafness with

tinnitus was recorded in this case series, though the lit-

erature reports an intrinsic relationship between hypo-

thyroidism and Meniere’s disease (a recent study quotes

a prevalence of 32%) [5].

Interpretations of these results must take into consid-

eration the limitations of our analysis. As data from a

single tertiary health care centre was used, it reflects the

experience of our geographical area and may not be gen-

eralized. Information from observational studies can be

subject to potential biases (e.g. selection bias) and con-

founding. Critics may contend that 6 months follow-up

period is short. Furthermore, the results were not ascer-

tained blindly. Last but not the least; we were unable to

discern the reason for this decreased sensorineural hear-

ing loss in goitrous hypothyroidism. This could be due to

the demographic profile of our patients. But then the au-

thors would like to emphasise that the very cause of

hearing loss in hypothyroidism is debatable and contro-

versial. Nevertheless, the strength of this study lies in its

prospective character and independent statistical valida-

tion, which allowed for accurate assessment of data with-

out depending upon recalled information in accordance

with evidence based medicine. The authors would like to

highlight that this study represents the largest series of

patients on hypothyroidism. The true value of this study

in context of existing literature lies in the audiological

evaluation of patients belonging to the subgroup of goi-

trous hypothyroid, hitherto unreported in medical litera-

ture.

5. Conclusion

In conclusion, the patients of goitrous hypothyroidism

have a lower rate of sensorineural hearing loss as com-

pared with other patients of hypothyroidism. Further, this

study delineates a definitive role of L-thyroxine therapy

in improvement of hearing in patients suffering from

goitrous hypothyroidism. We believe that conclusions of

this study can serve as a guide for future research on the

cited subject.

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