Abnormal thyroid hormones and non-thyroidal illness syndrome in obstructive sleep apnea, and effects of CPAP treatment.
In obstructive sleep apnea (OSA), while both hypothyroidism and hyperthyroidism have been studied, the occurrence of non-thyroidal illness syndrome (NTIS) (normal thyroid stimulating hormone [TSH] with low triiodotironine) has not been investigated. We explored the occurrence of NTIS in patients with moderate to severe OSA and its relationship to the severity of nocturnal respiratory disorders. We also studied the occurrence of subclinical hypothyroidism (SH, ie, high TSH with normal thyroxine) in OSA and changes in circulating TSH, free triiodotironine (fT3) and free thyroxine (fT4) after CPAP treatment.



After a nocturnal respiratory polysomnography, 125 consecutive patients with moderate to severe OSA and 60 control subjects with normal nocturnal respiration were recruited. Morning circulating TSH, fT3, and fT4 were measured in all subjects. In a subsample of patients, nocturnal polysomnography and hormonal determinations were repeated after CPAP treatment for five months.



NTIS was found in 13 (10.4%), and SH in ten (8%) OSA subjects, but not in any control subjects. Patients with NTIS showed worse mean nocturnal oxygen saturation and time with saturation <90% (both p < 0.001). After treatment, NTIS subjects (n = 13) showed an increase in fT3 (p < 0.001) to the normal range, and SH subjects (n = 6) a slight decrease in TSH (p = 0.01). In the patients with normal hormones before treatment (n = 45), no change was observed.



NTIS may occur in OSA patients with severe nocturnal hypoxemia. OSA treatment is followed by an improvement in TSH in patients with abnormal baseline levels of this hormone, and by recovery of NTIS.
Department of Respiratory Pathophysiology, "Mariano Santo" Hospital, Cosenza, Italy.
Albino
A
Petrone
Department of Pneumology, Fondazione Policlinico Universitario Agostino Gemelli, Catholic University of the Sacred Heart, Rome, Italy.
Flaminio
F
Mormile
Department of Respiratory Pathophysiology, "Mariano Santo" Hospital, Cosenza, Italy.
Giacomo
G
Bruni
Department of Emergengy Medicine, "San Francesco" Hospital, Paola (CS), Italy.
Michela
M
Quartieri
DIBIMIS, University of Palermo, Palermo, Italy; Institute of Biomedicine and Molecular Immunology, National Research Council, Palermo, Italy.
Maria R
MR
Bonsignore
Institute of Biomedicine and Molecular Immunology, National Research Council, Palermo, Italy. Electronic address: oreste.marrone@ibim.cnr.it.
Oreste
O
Marrone
D016022:Case-Control Studies; D045422:Continuous Positive Airway Pressure; D005067:Euthyroid Sick Syndromes / Q000150:complications / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D020181:Sleep Apnea, Obstructive / Q000150:complications / Q000503:physiopathology* / Q000628:therapy; D013963:Thyroid Hormones / Q000097:blood* / Q000502:physiology; D013974:Thyroxine / Q000097:blood / Q000502:physiology; D014284:Triiodothyronine / Q000097:blood / Q000502:physiology
D013963:Thyroid Hormones; D014284:Triiodothyronine; D013974:Thyroxine
Euthyroid sick syndrome; Hypoxemia; Obstructive sleep apnea; Subclinical hypothyroidism; Thyroid hormones; Thyroid stimulating hormone