Unsuspected thyrotoxicosis and hyperemesis gravidarum in Asian women

Comparison of thyroid function in pregnant and non-pregnant Asian and western Caucasian women

BACKGROUND

Gestational thyrotoxicosis may be more prevalent in Asian women.

METHODS

We have measured thyroid function, ferritin and bone specific alkaline phosphatase (BALP) as peripheral markers of thyroid function and hCG in Asian and western Caucasian women in non-pregnant and early pregnancy.

RESULTS

TSH was lower in Asian women in non-pregnancy but not during normal pregnancy and this may reflect increased sensitivity of the thyroid gland to thyroid stimulation in the Asian population. No ethnic difference was found in FT3, FT4 or hCG but ferritin was lower and BALP higher in Asian women whether pregnant or not and this may be a reflection of iron balance and vitamin D status.

CONCLUSIONS

We found during normal pregnancy that dynamic patterns of change for thyroid hormones and hCG are not different in Asian and western Caucasian women. We have developed gestation related reference intervals, which are a pre-requisite to the study of ethnic differences in gestation thyrotoxicosis in pregnancy.

[Is there a relationship between hyperemesis gravidarum and hyperthyroidism?]

This retrospective study evaluates the incidence and degree of thyroidal stimulation in patients with hyperemesis, and the correlation between thyroid function, the hCG level and the severity of the hyperemesis gravidarum. The role of antithyroidea is discussed in patients with a gestational hyperthyroidism. The degree of thyroid stimulation on the outcome of the pregnancy was studied. At admission hCG, TSH, FT4, FT3, TSI, anti-TPO and anti-Tg were determined. The severity of the hyperemesis gravidarum was evaluated by the degree of ketonuria, % weight loss, and the electrolytes and the liver function disorders. An ultrasound to confirm the gestational age and to exclude a multiple pregnancy or a trophoblastic disease was carried out.

RESULTS

In a period of 1 January '91 to 31 January '94, 48 hyperemesis gravidarumpatients were admitted at the maternity. 22.9% of the hyperemesispatients had thyroid stimulation; 4 patients had a decreased TSH and an increased FT4 (group 2) and 7 patients had a decreased TSH, an increased FT4 and FT3 (group 3). The age of the mother, the parity and the gestational age at admission are comparable, and do not differ from the patients without thyroid disorders (group 1). Parameters, determining the severity of hyperemesis gravidarum, are not significantly different in the 3 groups. Treatment with antithyroidea in the group with proven hyperthyroidism (decreased TSH, increased FT4 and FT3) does not only lead to normalisation of the thyroid tests, but also to an improvement of the symptomatology. The gestational age at delivery and the birthweight of the babies are comparable in the 3 groups.

CONCLUSION

In patients admitted with hyperemesis gravidarum, we found 23% of the women to present a thyroid stimulation. This hyperthyroidism differs from the auto-immune hyperthyroidism, i.e. the patients have no thyroid antibodies, no classic clinical signs of thyrothoxicosis. Probably, the absolute hCG concentration and its biological activity plays a crucial role in the thyroid stimulation. This degree of thyroid stimulation has no influence on the severity of the hyperemesis gravidarum, neither on the outcome of the pregnancy.