[Thyroid function and thyroid autoimmunity at the late pregnancy: data from 664 pregnant women].
OBJECTIVE
To study the prevalence of thyroid diseases, as well as characteristics of the disease spectrum and thyroid autoimmunity in women at the end of pregnancy.


METHODS
Six hundred and sixty-four pregnant women (pregnancy group) and 276 non-pregnant women (control group) were enrolled in the study. Serum thyrotropin (TSH), thyroid peroxidase antibody (TPOAb), free T(3) (FT(3)) and free T(4) (FT(4)) were measured by high-sensitive immunochemiluminescent assay, and urinary iodine was also examined at the end of pregnancy. Overt hyperthyroidism was diagnosed when both TSH < 0.3 mU/L and FT(4) and/or FT(3) levels were elevated. Subclinical hyperthyroidism was diagnosed when TSH < 0.3 mU/L with normal FT(4) and FT(3) levels. The diagnostic criteria for overt hypothyroidism was TSH > 4.8 mU/L accompanied by decreased FT(4), and for subclinical hypothyroidism was TSH > 4.8 mU/L with normal FT(4) and FT(3) levels.


RESULTS
(1) The median urinary iodine (MUI) of pregnancy group was 201.5 microg/L, and that of control group was 196.0 microg/L (P > 0.05). Women in the two groups were iodine-adequate. (2) The overall prevalence of thyroid diseases in pregnancy group and control group was 7.8% (52/664) and 6.9% (19/276), respectively (P > 0.05). (3) As for the diseases pattern, there were obvious differences between the two groups. In pregnancy group, the prevalence of hyperthyroidism was lower than that of hypothyroidism (1.1% vs 6.8%, P < 0.01). In control group, the prevalence of hyperthyroidism and hypothyroidism was 4.7% and 2.2%, respectively (P > 0.05). Compared with control group, the prevalence of hyperthyroidism in pregnancy group was much lower (1.1% vs 4.7%, P < 0.01), mainly due to the decrease of overt hyperthyroidism; whereas, the increment of subclinical hypothyroidism resulted in the higher prevalence of hypothyroidism in pregnancy group (6.8% vs 2.2%, P = 0.01). (4) The median TSH level of the healthy women in pregnancy group was significantly higher than that in control group (2.50 vs 1.54 mU/L, P < 0.01). The positive rate of TPOAb in pregnancy women was lower than that in non-pregnancy women (3.3% vs 9.4%, P < 0.01).


CONCLUSIONS
At the end of pregnancy, hypothyroidism accounts for most thyroid diseases. Thyroid autoimmunity is suppressed.
Guan
Hai-xia
HX
Department of Endocrinology, First Affiliated Hospital of China Medical University, Shenyang 110001, China.
Li
Chen-yang
CY
Li
Yu-shu
YS
Fan
Chen-ling
CL
Teng
Ying
Y
Ouyang
Yu-hong
YH
Cong
Qi
Q
Teng
Wei-ping
WP
D000328:Adult; D001323:Autoantibodies / Q000097:blood*; D015551:Autoimmunity; D002681:China / Q000453:epidemiology; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000453:epidemiology / Q000276:immunology / Q000503:physiopathology; D007453:Iodide Peroxidase / Q000276:immunology; D011247:Pregnancy; D011248:Pregnancy Complications / Q000097:blood / Q000276:immunology / Q000503:physiopathology; D011263:Pregnancy Trimester, Third; D015995:Prevalence; D013959:Thyroid Diseases / Q000453:epidemiology / Q000276:immunology / Q000503:physiopathology; D013960:Thyroid Function Tests; D013961:Thyroid Gland / Q000276:immunology* / Q000503:physiopathology*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
D001323:Autoantibodies; D014284:Triiodothyronine; D013972:Thyrotropin; D007453:Iodide Peroxidase; D013974:Thyroxine