PPID, ACTH, and infertility in mares

In this study mares with fertility issues had an increase incidence of elevated ACTH levels suggestive of PPID. It would seem sensible that part of evaluation of mares with low fertility is a screening for PPID and if found positive, consider treatment for the condition. Pergolide remains the treatment of choice for PPID. Concerning the use of pergolide during pregnancy you can find reference to this statement, made in the drug insert of the human product Permax®:

Pergolide has been assigned to pregnancy category B by the FDA. Animal studies using high oral doses of pergolide have failed to reveal evidence of fetal harm. There are no controlled data in human pregnancy. Pergolide should only be used during pregnancy when need has been clearly established.

However, I see several problems with pergolide use during pregnancy. The first is pergolide, a dopaminergic drug, can suppress lactation, the second is long term effects on the foal are unknown. These questions need to be worked out before use during pregnancy can be recommended.

Relationship between endogenous plasma adrenocorticotropic hormone concentration and reproductive performance in Thoroughbred broodmares
J Vet Intern Med. 2021 May 24.
Authors
Takeru Tsuchiya 1 2 , Ryusuke Noda 3 , Hiroki Ikeda 3 , Masaya Maeda 3 , Fumio Sato 2 4
Affiliations

1 Northern Farm Tenei, Fukushima, Japan.
2 United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan.
3 Equine Medical Center, Hidaka Horse Breeders Association, Hokkaido, Japan.
4 Equine Research Institute, Japan Racing Association, Tochigi, Japan.

PMID: 34028083
DOI: 10.1111/jvim.16145

Abstract

Background: Pituitary pars intermedia dysfunction (PPID) is an endocrine disorder the clinical signs of which include infertility, but few reports have examined the relationship between PPID and reproductive performance in broodmares.

Hypothesis/objective: Broodmares with infertility of unknown etiology were screened for PPID using baseline endogenous plasma ACTH concentrations, and its relationship with subsequent reproductive performance was analyzed.

Animals: Sixty-seven Thoroughbred broodmares.

Methods: Adrenocorticotropic hormone concentrations were measured in autumn. The broodmares were divided into 3 groups based on endogenous plasma ACTH concentration (low, <50 pg/mL; intermediate 50-100 pg/mL; and high >100 pg/mL) as recommended by the Equine Endocrinology Group. We compared these results with those of other blood tests, clinical examinations, subsequent conception, and frequency of normal delivery.

Results: The numbers of horses per group (percentage) were 22 (32.8%), 20 (29.9%), and 25 (37.3%). The mean ± SD ages (years) were 11.1 ± 3.4, 12.1 ± 4.5, and 13.0 ± 4.3, with no significant difference among groups. Mean ± SD plasma cortisol concentrations (μg/dL) were 4.0 ± 1.6, 7.1 ± 1.4, and 7.6 ± 1.9, with the intermediate and high ACTH groups having significantly higher results than the low ACTH group (P < .001). Conception rates were 77.3%, 89.5%, and 56.5% and normal delivery rates were 77.2%, 84.2%, and 43.5% with the percentage of each significantly lower in the high ACTH group (P = .02, P = .008, respectively).

Conclusions and clinical importance: The study group of infertile broodmares may include horses with PPID. The reproductive performance of the high ACTH group was significantly lower than the other groups. Early diagnosis and treatment of infertile broodmares by screening plasma ACTH concentrations could help improve reproductive performance.

Keywords: ACTH; ECD; PPID; broodmare; fertility; horse; pregnancy.