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CASE REPORT
Year : 2016  |  Volume : 13  |  Issue : 2  |  Page : 83-85

Central sleep apnea in untreated hypothyroidism: A rare association


Department of Neurology, Comprehensive Centre for Sleep Disorders, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Thiruvananthapuram, Kerala, India

Date of Web Publication1-Jun-2016

Correspondence Address:
Dr. Sapna Erat Sreedharan
Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Thiruvananthapuram - 695 011, Kerala
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0973-0354.183275

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  Abstract 

Obstructive sleep apnea (OSA) has been reported with untreated hypothyroidism. Here, we report a young patient referred to us due to prolonged apneas detected during recovery from minor surgery done under a short-acting general anesthetic drug. Polysomnography (PSG) was suggestive of severe OSA with high central index. He was later found to have severe hypothyroidism. Thyroxine replacement for 3 months followed by a repeat PSG showed persisting severe OSA but with no central events. This case highlights the rare association of central sleep apnea in untreated hypothyroidism which can be easily overlooked.

Keywords: Central sleep apnea, hypothyroidism, polysomnography


How to cite this article:
Sreedharan SE, Agrawal P, Radhakrishnan A. Central sleep apnea in untreated hypothyroidism: A rare association. Thyroid Res Pract 2016;13:83-5

How to cite this URL:
Sreedharan SE, Agrawal P, Radhakrishnan A. Central sleep apnea in untreated hypothyroidism: A rare association. Thyroid Res Pract [serial online] 2016 [cited 2019 Oct 15];13:83-5. Available from: http://www.thetrp.net/text.asp?2016/13/2/83/183275


  Introduction Top


Prevalence of undetected hypothyroidism in obstructive sleep apnea (OSA) ranges from 1.6% to 11%.[1],[2],[3] Hypothyroidism often causes upper airway narrowing, but there are rare reports of central sleep apnea syndrome secondary to dysfunction of the respiratory control center in untreated hypothyroidism. Here, we report a young gentleman with hypothyroidism presenting with features of sleep disordered breathing (SDB), whose central events completely disappeared after L-thyroxine replacement.


  Case Report Top


A 39-year-old gentleman underwent septoplasty for deviated nasal septum under a short-acting intravenous general anesthetic agent. In the immediate postoperative period, he had a slow recovery from the effect of anesthetic agent, and the surgeon witnessed a few apneas with desaturation. Subsequently, he was referred to our sleep clinic for ruling out SDB. His family reported snoring of moderate severity for several years, but no witnessed apneas or nocturnal arousals with respiratory difficulty. He had mild excessive daytime sleepiness (EDS) quantified by Epworth sleepiness scale of 12. He had no vascular risk factors or history of substance abuse. Examination showed a moderately built individual with BMI 24.49 kg/cm 2, with a neck circumference of 38 cm, rest of the clinical examination being essentially normal.

He underwent an overnight polysomnography (PSG) (Bio-Logic Inc., Heinen and Lowentsein, Bad ems, Germany) which showed fragmented sleep with severe OSA (apnea-hypopnea index [AHI] - 41.2/h) with a high central index of 11.2/h [Figure 1]. His cardiac evaluation was normal. His thyroid profile showed hypothyroidism (thyroid-stimulating hormone 30 (normal 1–5 unit) with low free T3 and free T4). Considering the possibility of untreated hypothyroidism presenting as SDB, we initiated him on L-thyroxine replacement at a dose of 0.1 mg/day and followed him up with a repeat PSG at 3 months.
Figure 1: Polysomnography showing multiple central sleep apneas with arousals

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At 3 months, he denied any EDS (Epworth sleepiness scale 8 only) and was feeling more energetic at workplace. The thyroid profile showed a euthyroid state. Repeat PSG showed fragmented sleep with severe OSA (AHI 39.3 events/h), but the central events had altogether disappeared [Figure 2]. After counseling, we initiated him of continuous positive airway pressure (CPAP) therapy, and he required PAP of 10 cm H2O for abolishing respiratory events. Currently at 9 months follow-up, he is asymptomatic, on CPAP and thyroxine replacement.
Figure 2: Polysomnography 3 months after thyroid hormone replacement and achieving euthyroid state shows severe degree of obstructive sleep apnea with no central events

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  Discussion Top


OSA is reported to have a high prevalence in the fifth and sixth decades of life with several authors describing a strong association with obesity and increased neck circumference.[4],[5] Untreated hypothyroidism also shares many features which increase the risk of OSA.[1] Furthermore, many symptoms of OSA such as EDS, snoring, and lethargy are also found in hypothyroidism making many authors suggest routine screening of all OSA subjects with thyroid function test.[6]

Pathophysiology of OSA in untreated hypothyroidism is multifactorial. Jha et al.,[7] proposed different mechanisms such as mucopolysaccharide deposition in the upper airways, central obesity, and myopathy involving pharyngeal dilators as contributing to the development of OSA in hypothyroidism. Our patient presented with severe OSA with high central index. Although the majority of authors have reported the association of hypothyroidism with OSA, only a few have reported central events.[8],[9] Dysfunction of respiratory control center has been found in a report where hypothyroid patient presented with central sleep apnea syndrome.[8] We treated our patient with L-thyroxine initially, with the disappearance of central events, but not obstructive events. Millman et al.,[8] reported the disappearance of CSA in their patient with thyroid hormone replacement. In a review on endocrine aspects of OSA, authors have reported improvement or even cure of patients with OSA on correction of endocrine abnormality.[10] In a series of five subjects with varying OSA severity and hypothyroidism, OSA improved at 4 months follow-up on thyroid replacement alone.[1] In an Indian series of 12 subjects with hypothyroidism and OSA, sleep abnormality was reversible in 10 subjects which was secondary to changes in the upper airway following thyroid hormone replacement.[7] In our patient, persisting severe OSA necessitated the use of CPAP, which has been reported by few others.[10]

We report this rare case to highlight few points pertinent to any treating physician but is often overlooked if one is not aware of it. One is the rare association of central sleep apnea with untreated hypothyroidism. Furthermore, the fact that it is completely reversible with timely hormone replacement. All the more, this has been seldom reported in literature. Therefore, in hypothyroid patients with SDB, supplementing thyroid hormone is worth a trial before proceeding with CPAP therapy.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Lin CC, Tsan KW, Chen PJ. The relationship between sleep apnea syndrome and hypothyroidism. Chest 1992;102:1663-7.  Back to cited text no. 1
    
2.
Popovici I, Khawaja I. Efficacy of thyroid function tests in patients suspected of having obstructive sleep apnea. Chest 1997;112:149S.  Back to cited text no. 2
    
3.
Orr WC, Males JL, Imes NK. Myxedema and obstructive sleep apnea. Am J Med 1981;70:1061-6.  Back to cited text no. 3
[PUBMED]    
4.
Young T, Palta M, Dempsey J, Skatrud J, Weber S, Badr S. The occurrence of sleep-disordered breathing among middle-aged adults. N Engl J Med 1993;328:1230-5.  Back to cited text no. 4
    
5.
Samson P, Casey KR, Knepler J, Panos RJ. Clinical characteristics, comorbidities, and response to treatment of veterans with obstructive sleep apnea, Cincinnati Veterans Affairs Medical Center, 2005-2007. Prev Chronic Dis 2012;9:E46.  Back to cited text no. 5
    
6.
Hira HS, Sibal L. Sleep apnea syndrome among patients with hypothyroidism. J Assoc Physicians India 1999;47:615-8.  Back to cited text no. 6
    
7.
Jha A, Sharma SK, Tandon N, Lakshmy R, Kadhiravan T, Handa KK, et al. Thyroxine replacement therapy reverses sleep-disordered breathing in patients with primary hypothyroidism. Sleep Med 2006;7:55-61.  Back to cited text no. 7
    
8.
Millman RP, Bevilacqua J, Peterson DD, Pack AI. Central sleep apnea in hypothyroidism. Am Rev Respir Dis 1983;127:504-7.  Back to cited text no. 8
[PUBMED]    
9.
Kittle WM, Chaudhary BA. Sleep apnea and hypothyroidism. South Med J 1988;81:1421-5.  Back to cited text no. 9
    
10.
Attal P, Chanson P. Endocrine aspects of obstructive sleep apnea. J Clin Endocrinol Metab 2010;95:483-95.  Back to cited text no. 10
    


    Figures

  [Figure 1], [Figure 2]


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