Thyrotoxicosis and hyperemesis gravidarum associated with a serum activity which stimulates human thyroid cells in vitro.

OBJECTIVE

To investigate in-vitro thyroid stimulatory activity in the serum of patients with hyperemesis gravidarum and thyrotoxicosis.

DESIGN

Serum from hyperthyroid patients was incubated with cultures of human thyroid cells. Attempts were made to neutralize stimulatory activity with antisera to hCG.

PATIENTS: Five patients presenting in early pregnancy with hyperemesis and thyrotoxicosis.

MEASUREMENTS: Serum concentrations of thyroid hormones (total and free), TSH and hCG. Accumulation of extracellular cAMP in response to serum.

RESULTS

All five patients had biochemical hyperthyroidism with no evidence of an underlying autoimmune disease. The mean cAMP accumulation over 4 hours with sera from 12 non-pregnant controls was 130.6 (121.8-142.8), from 12 pregnant controls 132.4 (118.1-143.8), compared with values of 144.7, 159.1, 166.2, 178.9 and 320.5 for the thyrotoxic patients. The stimulatory activity could not be neutralized by addition of anti-hCG or by depleting the sera of hCG.

CONCLUSIONS

Thyrotoxicosis may present with hyperemesis in early pregnancy. Clinical and biochemical features may be masked by the pregnancy or by the intercurrent illness. The hypothesis that hCG is a thyroid stimulator in patients with hyperemesis gravidarum is not supported by the immuno-neutralization data in this study.