Sleep development in children with congenital and acquired hypothyroidism

Cyclic alternating pattern in infants with congenital hypothyroidism

Congenital hypothyroidism is defined as thyroid hormone deficiency present at birth which is crucial for brain development. Recently, the cyclic alternating pattern, a rhythm present in electroencephalography recordings in non-Rapid eye movement sleep, has been related to brain development and cognition in different pediatric conditions. Therefore, we evaluated the cyclic alternating pattern rate in infants with congenital hypothyroidism, thyroxine supplementation, and healthy controls. The parameters of the cyclic alternating pattern were evaluated in 19 healthy infants (10 female, mean age 25.5 ± 15.5 months) and 21 infants diagnosed with congenital hypothyroidism (19 female, mean age 24.3 ± 19.0 months). We considered the transient electro-cortical activations (phase A of the cycle) in non-Rapid eye movement sleep and the subdivisions of the A phase in: A1, A2 and A3, based on their frequency content. All subjects were subjected to polysomnography recording in a standard laboratory setting. Sleep data were stored computer following the International 10-20 System. Data showed that congenital hypothyroidism infants exhibited higher frequency of central apnea, hypopnea, and arousals in comparison to controls. Particularly, central apnea index decreased with age in the control group but not in congenital hypothyroidism group. Regarding to cyclic alternating pattern measurements, congenital hypothyroidism infants exhibit a higher frequency in the percentage of A3 subtype (electroencephalographic desynchrony) and conversely a lower percentage of A1 subtype (electroencephalographic synchrony), than healthy infants. An important finding of this study is the positive correlation between A1 mean duration and age, which is bigger in control group than in congenital hypothyroidism group (time duration in control group (0.52 s/month) versus congenital hypothyroidism group (0.1 s/month). Infants with congenital hypothyroidism showed an increase of A3 subtype, of central apnea, and of arousals. The reduction of percentage and mean duration of A1 subtype could be a valuable indicator of sleep development in patients with congenital hypothyroidism and healthy infants.

Polysomnographic features in infants with early diagnosis of congenital hypothyroidism

Thyroid hormones play a major role in the maturation process of the brain. Currently, congenital hypothyroidism is detected by mass screening. The impact of this early hormonal deficiency on the organization of the sleep pattern is not known. In this study, the polysomnographic features in children diagnosed with congenital hypothyroidism were analyzed. Children were detected by mass population screening and the hormonal replacement therapy starts immediately. Children's age ranged between 1.5 and 18 months of age. The duration of hormonal treatment before sleep recordings varied between 8 days and 17 months. Children were polysomnographically recorded in the morning, for at least 2h, obtaining more than one sleep cycle. Results showed a high prevalence of females (5/1) in the group studied. A high proportion of infants (43%) displayed central apnea in different degrees (mild, moderate and severe) as well as hypopnea (83%), mainly in subjects around 4 and 8 months of age. The proportion of infants displaying central apnea decreases as age increases. In addition, indeterminate (light) sleep increase and quiet (slow wave) sleep decrease significantly regardless of age and treatment. The percentage of REM sleep correlated positively with the age of the child at the beginning of the treatment, and negatively with their age at the time of the study. These data indicate that congenital hypothyroidism facilitates the presence of central sleep apnea. The decrease of these respiratory alterations correlates with the increase of the hormonal replacement therapy. It seems that sleep respiratory alterations in congenital hypothyroidism are linked to brain maturation processes in which thyroid hormones play a major role.