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.