So I just started HCG monotherapy (500 iu three times a week) and was wondering about HCG’s half life and pharmacology parameters. I found a few relevant studies (and have attached their pdfs). Check them out, they are interesting, especially the third study. Do you guys have any other info (peer reviewed studies) pertaining to this topic?

1. Pharmacokinetics of human chorionic gonadotropin after
i.m. administration in goats (Capra hircus) (**I know goats lol)

The present investigation addresses the pharmacokinetics of human chorionic gonadotropin (hCG), intramuscularly (i.m.) administered to goats. Nine pluriparous does of the Boer goat breed, 2–6 years of age and weighing 45–60 kg, were administered 500 IU hCG (2 ml Chorulon) deep into the thigh musculature 18 h after superovulatory FSH treatment. Blood samples were drawn from the jugular vein at 2 h intervals for the first 24 h, at 6 h intervals until 42 h, and at 12 h intervals until 114 h after administration. After centrifugation, plasma hCG concentrations were determined by electrochemiluminescence immunoassay. Pharmacokinetical parameters were as follows: lag time, 0.4 (S.E.M. 0.1) h; absorption rate constant, 0.34 (S.E.M. 0.002) h; absorption half-life, 2.7 (S.E.M. 0.5) h; elimination rate constant, 0.02 (S.E.M. 0.002) h; biological half-life, 39.4 (S.E.M. 5.1) h; and apparent volume of distribution, 16.9 (S.E.M. 4.3) l. The plasma hCG profile was characterized by an absorption phase of 11.6 (S.E.M. 1.8) h and an elimination phase of 70.0 (S.E.M. 9.8) h, with considerable individual
variation in bioavailability and pharmacokinetical parameters. Biological half-life was negatively correlated (P!0.05) with peak concentration (rZK0.76), absorption rate constant (rZK0.78), and elimination rate constant (rZK0.87). The results indicate that after rapid absorption, hCG remains in the circulation for an extended period. This has totaken into account when assessing the stimulatory
response to hCG treatment on an ovarian level.

2. Bioavailability of hCG after intramuscular or subcutaneous
injection in obese and non-obese women

(** this is done in women, but gives a good comparison between IM injection vs. Sub Q injection)

BACKGROUND: Obese women require higher gonadotrophin doses for ovarian stimulation and to trigger ovulation. The bioavailability of a drug is affected by its route of administration. Herein, the bioavailability of hCG was
compared after intramuscular (i.m.) or subcutaneous (s.c.) injection in obese and non-obese women. METHODS: Twenty four Chinese women, 12 with a body mass index (BMI) >28 kg/m2 and 12 with a BMI of 20±25 kg/m2 were
recruited as the obese and non-obese groups respectively. A single hCG injection was given intramuscularly on one occasion, and subcutaneously on a second occasion, separated by 4 weeks. Blood samples were taken at intervals for
the pharmacokinetic study of hCG. RESULTS: Examination of the hCG plasma concentration±time curve showed the area under the curve (AUC) and maximum concentration (Cmax) of hCG to be signi®cantly higher after i.m.
injection than after s.c. injection in both the obese and non-obese groups. However, the AUC and Cmax values in obese women were signi®cantly lower than in non-obese women, irrespective of whether i.m. or s.c. dosing was
employed. CONCLUSIONS: Intramuscular dosing of hCG provided better bioavailability than s.c. dosing, but bioavailability was signi®cantly less in obese women than in non-obese women.

3. Pharmacokinetics and pharmacodynamics of recombinant human chorionic gonadotrophin in healthy male and female volunteers.

(*** this one was the most interesting and relevant)


The pharmacokinetics and pharmacodynamics of recombinant human chorionic gonadotrophin (rHCG) were investigated in three studies of healthy volunteers. After single intravenous doses of 25,250 and 1000 µg, rHCG and urinary HCG (uHCG) showed linear pharmacokinetics described by a bi-exponential model, although the area under the curve (AUC) for uHCG was ∼29% lower than for rHCG. After intramuscular or subcutaneous administration (absolute bioavailability, 40-50% for both), rHCG pharmacokinetics could be described by a first-order absorption, one-compartment model. During multiple subcutaneous dosing, the amount of HCG increased by ∼1.7-fold. A comparison of liquid and freeze-dried rHCG and freeze-dried uHCG showed pharmacokinetic bioequivalence. In down-regulated male subjects, single doses of 125 µg rHCG, given intravenously, intramuscularly or subcutaneously, produced comparable increases in serum testosterone , inhibin and 17βoestradiol, with little further increase during repeated subcutaneous administration (in female subjects, this produced a sustained comparable increase in serum androstenedione and testosterone concentrations). In conclusion, the pharmacokinetics and pharmacodynamics of rHCG are similar to those of uHCG and are not affected by the use of different formulations. In healthy subjects, rHCG produces pharmacodynamic responses consistent with HCG physiology and is suitable for use in the same clinical indications as uHCG. The secured source and high purity of rHCG may offer important advantages.

Some interesting notes about the third study: the study used high doses of HCG 2500 ius. The half life was about 30 hours and was not significantly dependent upon administration method (IV, IM, Sub Q). Peak testosterone was achieved 84 hours after a single dose of 2500 iu. Peak OEstradiol 17b was found at 96 hours after a single 2500iu dose and sub Q yielded slightly higher peak OE 17b levels 194 vs 177 (IM) vs 122 (IV).

***Well it looks like the forum will not let me upload the studies because they are all over 100 kb in size and the forum limit is 100 kb. If you have access to academic journal databases type the study in and check them out, especially the third one.