[Persistent low hCG levels beyond pregnancy: report of two cases and review of the literature].

Unexpected finding or persistence of low human chorionic gonadotropin (hCG) levels is not a rare situation. It requires a clinico-biological approach in order to avoid misunderstandings that could lead to inappropriate diagnostic or therapeutic attitudes. Beyond pregnancy, persistent low levels of hCG may be associated with various benign and malignant conditions, i.e. quiescent gestational trophoblastic disease (QTD), raised pituitary hCG or false positive elevation caused by circulating heterophile antibodies. We report the cases of two non-pregnant patients with low serum hCG. In the first case, hCG levels raised during several years following a spontaneous abortion. The likelihood of heterophilic antibodies interference was ruled out and extensive clinical investigation excluded the presence of a tumour. The diagnosis was QTD. In the second case, elevated hCG came to light as an incidental finding in a women with chronic renal failure and led the clinicians to question the laboratory. The cause was probably an increase in pituitary hCG consecutive to terminal renal failure. These cases illustrate the importance of understanding the biology of the hCG and the causes of its persistent low elevation, which are reviewed in this article. It is essential to demonstrate clinically the presence of a tumour in order to avoid unnecessary and ineffective chemotherapy and/or hysterectomy.