title: Sex hormone binding globulin and free levonorgestrel index in the first week after insertion of Norplant implants.
abstract: Levonorgestrel has an inhibitory effect on sex hormone binding globulin (SHBG). This decrease in SHBG leads to an increase in the free levonorgestrel index (FLI), which has a stronger biological effect. The interaction between serum levels of levonorgestrel and SHBG in long-term users of Norplant implants has been described. This study was designed to understand the same interaction immediately after the insertion of the implants, in a group of 16 women, sampled at 0 and 6 h and at 1, 3, and 7 days after Norplant implant insertion. Peak serum levonorgestrel levels were achieved at 24 h after insertion, remaining stable on day 3 and decreasing by > 10% by day 7. SHBG did not change during the first 24 h, but decreased by 19% and 60% on days 3 and 7, respectively. FLI more than doubled from day 1 to day 7 after insertion. The large decrease in SHBG and doubling of FLI is not followed by a similar reduction in levonorgestrel, which is hard to explain without an increase in the release rate of the steroid from the capsule.
authors.affiliation: Biomedical Research Department, PROFAMILIA, Santo Domingo, Dominican Republic.
authors.forename: F
authors.initials: F
authors.lastname: Alvarez
authors.forename: V
authors.initials: V
authors.lastname: Brache
authors.forename: A S
authors.initials: AS
authors.lastname: Tejada
authors.forename: L
authors.initials: L
authors.lastname: Cochon
authors.forename: A
authors.initials: A
authors.lastname: Faundes
mesh_terms: D003271:Contraceptive Agents, Female; D004343:Drug Implants; D005260:Female; D006801:Humans; D007700:Kinetics; D016912:Levonorgestrel / Q000008:administration & dosage / Q000009:adverse effects* / Q000097:blood*; D011446:Prospective Studies; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism*
chemical_list: D003271:Contraceptive Agents, Female; D004343:Drug Implants; D012738:Sex Hormone-Binding Globulin; D016912:Levonorgestrel