Science Digest: What is the potential for human chorionic gonadotropin treatment in guinea pigs with bilateral non-pruritic alopecia caused by follicular cysts?
14 March 2025
Ovarian cysts are a common condition in female guinea pigs and include follicular cysts, serous cysts and para-ovarian cysts1. The prevalence of follicular cysts varies from 0 to 22%, with affected guinea pigs displaying a range of clinical signs, discomfort and reduced wellbeing1.
While surgical options such as ovariectomy or ovariohysterectomy offer a definitive solution for both follicular and serous cysts, less invasive, hormonal therapy is a potential alternative, but research is lacking1. There have been no studies on the effect of human chorionic gonadotropin (hCG) to treat follicular cysts in guinea pigs, although it has shown promising results for treating follicular cysts in cows2.
A new study published in the Journal of Exotic Pet Medicine is the first clinical trial to evaluate the effects of hCG on bilateral non-pruritic alopecia in female guinea pigs with suspected follicular cysts1.
What did the study do?
Seven female guinea pigs aged 23-60 months presenting with bilateral non-pruritic alopecia at the University Hospital for Companion Animals, Copenhagen, were included. Guinea pigs were administered hCG at 100 IU/kg subcutaneously once a week for three weeks (on days 1, 8, and 15 of the study). Patients were monitored for eight weeks, and during each visit, a clinical examination was performed and information obtained from the owner on the animal’s behaviour, appetite, thirst, and any pruritus. Transabdominal ultrasound was performed on days 1, 15, and 28. The therapeutic response was assessed solely on the resolution of bilateral non-pruritic alopecia, although partial coat regrowth was also deemed a successful response.
What were the key findings?
HCG treatment was deemed successful for all patients, with all showing resolution of clinical signs. Hair regrowth was observed by day 8 in two individuals, by day 15 in three individuals and by day 28 in two individuals. As well as bilateral non-pruritic alopecia, clinical signs included mammary hyperkeratosis, absence of vaginal membrane for > 5 days (the first time this has been reported in guinea pigs with suspected follicular cysts), behavioural change and weight loss. An improvement in at least one clinical sign was seen after the first hCG injection in six out of seven guinea pigs and positive behavioural changes were seen in four guinea pigs. In six guinea pigs, body weight increased during the treatment. The treatment didn’t significantly change the size of the ovary and ovarian cysts, so it’s important to inform owners that larger cysts are not expected to reduce in size with hCG treatment. Adverse effects were minimal, with only a mild injection site reaction in one guinea pig after the third injection. The study was limited by the small sample size (7 guinea pigs), the lack of a control group and the observation period being restricted to 56 days.
The decision to use hCG instead of surgery should be tailored to each case, taking several factors into account: 1) the size of any suspected serous cysts and whether they appear to cause discomfort, as hCG treatment is unlikely to reduce them, 2) the presence of ovarian tumours or uterine masses, where OHE could be locally curative, 3) the risk of anaesthesia and surgery, and 4) any co-morbidities such as cardiovascular disease, which increase the risk of anaesthesia and may also indicate a poor overall prognosis.
Take home message
HCG treatment offers a less invasive alternative to ovariohysterectomy in guinea pigs with bilateral non-pruritic alopecia consistent with follicular cysts, with minimal adverse effects. The decision between hCG treatment or ovariohysterectomy should be individualised, taking into consideration any large serous cysts and potential co-morbidities. Further, long-term studies on larger populations are needed to confirm these findings and assess the risk of recurrence and long-term effects.
Reference
1Vildershøj C, Müller AV, Rueløkke ML & Bojsen-Møller Secher J (2025) Human chorionic gonadotropin treatment of bilateral non-pruritic alopecia in seven female guinea pigs. Journal of Exotic Pet Medicine. https://doi.org/10.1053/j.jepm.2025.02.001
De Rensis F, López-Gatius F, GarcÃa-Ispierto I & Techakumpu M (2010) Clinical use of human chorionic gonadotropin in dairy cows: An update. Theriogenology. 73 (8), 1001-1008. https://doi.org/10.1016/j.theriogenology.2009.11.027