Pharmacology of estrogens and progestogens: influence of different routes of administration, CLIMACTERIC 2005;8(Suppl 1):3–63
"Since, after 6 months, the levels are still elevated, reimplantation of new pellets may lead to an accumulation and to higher estradiol levels."
Levels tested before second pellet was implanted may have not peaked yet so that when second pellet was implanted, levels further increased from both pellets.