Local Tissue Reaction to the Implantation of Crystals and Pellets of Estrogenic Hormone

Summary and Conclusions

The local tissue response to implanted crystals and pellets is a typical non-specific foreign body reaction. Following the implantation of crystals of a-estradiol and a-estradiol benzoate, the tissue surrounding the crystals responds by the formation of tiny nodules. In contrast to this type of reaction, a thick avascular capsule forms about the pellets of the implanted hormone. It is important to note that the epidermis overlying the implants showed no evidence of cellular atypism and, similarly, in no instance did the subcutaneous tissues in contact with, and adjacent to, the implanted hormone show any abnormal cellular proliferation.

A significant observation which emerges from this study is the probable effect that the thick avascular capsule has on the absorption rate of the estrogenic substances employed. It was noted that the crystals had a strikingly more prolonged therapeutic and physiologic effect than the pellets composed of the same estrogenic substance and of comparable weight. It would appear, therefore, that the capsule might have a marked retarding effect on the rate of absorption of the hormone. Apparently, with the passage of time, the absorption rate is progressively diminished by the growing thickness of the capsule around the pellet. After a period of approximately 3 months, absorption is either completely stopped or so reduced as to have no demonstrable physiologic or therapeutic effect. It seems, therefore, that for purposes of implantation, pellets of a-estradiol and a-estradiol benzoate are not as efficient as crystals of the same chemical constitution.