Obstructive sleep apnea syndrome and hypothyroidism - merely concurrence or causal association?

Łukasz Mokros,Agata Gabryelska,Wojciech Kuczyński,Piotr Białasiewicz

doi:10.5603/piap.2016.0038

Abstract

The prevalence of obstructive sleep apnea-hypopnea syndrome (OSAHS) ranges from 4 to 7% in men and from 2 to 5% in women. Its deleterious consequences such as traffic accidents, cardiovascular complications increasing morbidity and mortality, make it a major health problem. Apart from obesity (a major risk factor for OSAHS), hypothyroid patients are prone to reveal this phenotype. Although hypothyroidism seems an acknowledged risk factor for OSAHS, some authors report the lack of clinically relevant association. The argument partly depends on the increased prevalence of hypothyroidism in OSAHS patients, but the epidemiological data is limited and somehow inconsistent; even less is known about sub-clinical hypothyroidism in OSAHS patients. Even if frequency of overt and sub-clinical hypothyroidism in OSAHS patients is comparable to the general population, screening for it seems beneficial, as hormone replacement therapy may improve sleep disordered breathing. Unfortunately, this favorable outcome was found only in a few studies with limited number of patients with hypothyroidism. Yet, despite the lack of international guidelines and no large multicentre studies on the topic available, we think that TSH screening might prove beneficial in vast majority of OSAHS patients.

Highlights

Obstructive sleep apnea — hypopnea syndrome (OSAHS) is a chronic condition, characterized by recurrent pauses in breathing during sleep
Authors suggested that the prevalence of newly diagnosed cases of clinical hypothyroidism in OSAHS patients was too low to justify routine screening, unless hypothyroidism was suspected on the basis of symptoms or signs [12]
As there exists an overlap in clinical presentation of primary OSAHS and hypothyroidism, it is currently discussed whether screening for hypothyroidism is needed

Summary

Association of OSAHS and hypothyroidism

There is a great variance in reported prevalence of hypothyroidism among patients with OSAHS. Out of 124 patients, who were diagnosed with OSAHS (69%), only 3 were discovered to have previously undiagnosed hypothyroidism These patients, were not included in the group treated with CPAP for the primary sleep apnea. Rosen D. in his study presents a case of 5-year old child with Down Syndrome diagnosed with mild to moderate OSAHS To this diagnosis, biochemical screening for hypothyroidism was performed. Authors suggested that the prevalence of newly diagnosed cases of clinical hypothyroidism in OSAHS patients was too low to justify routine screening, unless hypothyroidism was suspected on the basis of symptoms or signs [12]. Another study, whose findings support screening for sub-clinical and clinical hypothyroidism was conducted by Ozcan et al It included 203 patients with mild to severe OSAHS. This statement is controversial and should be treated merely as a hypothesis and not a conclusion supported by results of the study

Putative mechanisms of the association between OSAHS and hypothyroidism

Findings

Conclusions