CIRCADIAN THYROTROPIN VARIATIONS ARE PRESERVED IN NORMAL PREGNANT-WOMEN

Serum thyrotropin (TSH) concentration circadian rhythm is abolished in many endocrine and nonendocrine diseases. In the present study we hav e measured serum TSH concentration over 24 h every 2 h in second and t hird trimester pregnant women. During the 24-h period, serum free thyr oxine and free triiodothyronine concentrations did not change signific antly. In contrast, serum TSH concentrations demonstrated significant circadian variations both in the second and third trimester pregnant w omen (p < 0.02 and p < 0.005, respectively). In summary, second and th ird trimester pregnancy is associated with a normal circadian TSH rhyt hm.