Circannual pattern of hypothalamic-pituitary-thyroid (HPT) function and mood during extended antarctic residence

The seasonal variation in thyroid function and mood was examined in 10 men and two women who spent the 1997 or 1998 austral winter at McMurdo Station, Antarctica. Serum samples of TSH, free T-3 and free T-4 were collected eac h month over a 10-month period (October-August), along with responses to th e Profile of Mood States (POMS) and the Center for Epidemiologic Studies - Depression (CES-D) Scale. Both TSH and mood (a summary score created from t he POMS depression, anger, fatigue and confusion subscales) exhibited a cir cannual pattern with peaks during the months of November and July and a tro ugh during the months of March and April. High levels of tension-anxiety an d confusion were preceded by declines in free T-3 and T-4. However, increas es in tension-anxiety and total mood disturbance also preceded a decline in free T-3 levels, suggesting a feedback of mood on T-3 levels. Levels of fr ee T-4 were independently associated with preceding increases in anger scor es, These results support the hypothesis that the symptoms characteristic o f the winter-over syndrome is a state of relative CNS hypothyroidism. This model of seasonal variation in thyroid function and mood also has implicati ons for an understanding of potential mechanisms underlying the association between latitude and SAD or S-SAD. (C) 2001 Elsevier Science Ltd. All righ ts reserved.