Effects of Short‐term Hyper‐ and Hypoprolactinaemia on Hormones of the Pituitary, Gonad and ‐Thyroid Axis and on Semen Quality in Male Beagles

Abstract

Effects of a short-term hyper- and hypoprolactinaemia on serum concentrations of LH, testosterone and semen quality in six male Beagles were investigated. Blood samples were collected at 3-day intervals for 12 weeks. The time span was divided into five 3-week periods: pre-treatment, metoclopramide (MCP) treatment (0.2 mg/kg orally three times daily), cabergoline (CAB) treatment (5 microg/kg orally once daily), post-treatment 1 and post-treatment 2. In the latter, only semen characteristics were evaluated. Semen parameters were analyzed once per week during the whole 15-week investigation time. At the end of each period, the effects of a single intravenous injection of thyrotropin-releasing hormone (TRH; 10 microg/kg) on the secretion of prolactin (PRL), LH, testosterone, thyroid-stimulating hormone and thyroxine (T4) were investigated. Pre-treatment serum PRL concentration increased under MCP (p < 0.05), followed by a decrease under CAB administration (p < 0.05). Luteinizing hormone and testosterone concentrations were not affected. Except for straight-line sperm velocity, semen quality did not differ between collection periods. A single iv TRH injection induced a significant PRL increase at 20 min in all experimental periods except during CAB treatment. Luteinizing hormone and testosterone did not show clear TRH-related changes. Basic T4 levels were significantly reduced after CAB treatment (p < 0.05). The results of the present study demonstrate that MCP-induced short-term hyperprolactinaemia in male beagles does not seriously affect the hypothalamo-pituitary axis and semen quality.

Meningeal CGRP‐Prolactin Interaction Evokes Female‐Specific Migraine Behavior

“…Our data suggest that peripherally‐restricted Prlr antagonists could be an option for the effects of PRL on the headache phase of attacks. While these therapeutic approaches may not be completely devoid of adverse effects, pharmacological reduction of pituitary PRL release is chronically prescribed to thousands of patients with hyperprolactinemia with minimal ill effects 59 and would likely only be contraindicated in women who are pregnant or nursing, both conditions where extensive drug restrictions are common. Targeting PRL signaling for migraine could ultimately represent one of the first sex/gender‐specific therapeutics for a neurological disorder and may pave the way for future approaches that would be designed to have efficacy only in females or males.…”

Pathogenesis of the crosstalk between reproductive function and stress in animals – part 2: Prolactin, thyroid, inflammation and oxidative stress

“…Hyperprolactinemia has been associated with reproductive disorder and infertility in humans (Maiter, 2022), in stallions (Giesecke et al, 2010) and in bitches (Ohtaki et al, 2020). Yet, the effect of hyperprolactinemia on reproduction seems to depend on its duration, in particular in male dogs (Koivisto et al, 2009). The main suspected reason by which hyperprolactinemia induces reproductive disorders and infertility is prolactin's ability to suppress the pulsatory GnRH release and subsequent follicle‐stimulating hormone and LH inhibition.…”