Prolonged ovarian acyclicity is associated with a higher likelihood of developing hyperprolactinemia in zoo female African elephants

Abstract

Hyperprolactinemia is a common disorder of the hypothalamic‐pituitary axis, and a cause of ovarian dysfunction in women. Currently, over half of non‐cycling African elephant females in North America also are hyperprolactinemic, suggesting a similar link between these two conditions may exist. The objective of this study was to determine the relationship between acyclicity and prolactin status by comparing mean prolactin concentrations of bi‐weekly samples collected over a 1‐year period in 2012 with 20 years of historical weekly progestagen data to assess cyclicity. Females were categorized as: 1) non‐cycling with an average prolactin concentration of 15 ng/ml or greater (HIGH; n = 17); 2) non‐cycling with an average prolactin concentration below 15 ng/ml (LOW; n = 16); and 3) typical temporal patterns of progestagen and prolactin secretion (NORMAL; n = 45), and evaluated based on length of time (in years) they had experienced ovarian inactivity. Results showed that the majority of HIGH prolactin elephants had been acyclic for at least 5 years, and in a number of cases (n = 9) for over 10 years. By contrast, most of the LOW prolactin elephants had experienced acyclicity for less than 5 years. Finally, there was a positive association between duration of acyclicity and mean prolactin concentrations, with an increase in the likelihood of having higher prolactin concentrations the longer an individual was acyclic. This study highlights the importance of longitudinal hormonal datasets to examine temporal changes in biological functioning and better understand the etiology of infertility problems.

Clinical health issues, reproductive hormones, and metabolic hormones associated with gut microbiome structure in African and Asian elephants

“…Bacteria associated to prolactin may be of interest in future studies due to the high incidence of hyperprolactinemia in captive African elephants in North America [ 14 , 38 , 43 ]. In African elephants, prolactin had linear correlations with 17 bacterial taxa and non-linear relationships with 31 bacterial taxa.…”

“…5 ). This suggests there are increases in bacterial relative abundance in hyperprolactinemic elephants that are not associated with lower concentrations of prolactin (hyperprolactinemia categorized as 15 ng/ml or greater) [ 38 , 112 ]. We do not know if bacterial abundance could contribute to the cause of hyperprolactinemia or be a by-product of it.…”

“…Acyclicity limits the ability of breeding programs to become self-sustaining. Acyclicity has been linked to chronically high levels of circulating prolactin (a pituitary disorder called hyperprolactinemia) with an increased probability of developing the longer the elephant is acyclic [ 14 , 38 ]. Additionally, high body mass index (BMI) and high body condition scores (BCS) have been linked to acyclicity [ 39 , 40 ].…”

Reproductive one health in primates

“…In most primates (with the notable exception of callitrichids), postpartum ovarian cyclicity is naturally inhibited during the first part of lactation by increased prolactin concentrations. However, excessively high prolactin concentration in nonlactating females has been associated with abnormal reproductive cycles in women (Capozzi et al, 2015; UpToDate, 2021) elephants (Prado et al, 2018) and gorillas (Chatfield et al, 2006). It is of note that in the case of gorillas, a later publications documented that gorillas normally have higher prolactin concentrations (49.9–93.7 ng/ml) than humans across the reproductive cycle, without apparent impact on fertility (Laughlin et al, 2008).…”