Effect of Ghrelin and Thyrotropin-releasing Hormone on Prolactin Secretion in Normal Women

Abstract

It is known that ghrelin stimulates the secretion of prolactin in women. The aim of this study was to examine the effect of exogenous thyrotropin-releasing hormone (TRH) on ghrelin-induced prolactin release. Ten healthy normally cycling women were studied in four menstrual cycles. The women were injected intravenously in late follicular phase (follicle size 16-17 mm) with a single dose of normal saline (cycle 1), ghrelin (1 microg/kg) (cycle 2), thyrotropin-releasing hormone (200 microg) (cycle 3), and ghrelin plus thyrotropin-releasing hormone (cycle 4). Blood samples in relation to saline or drugs injection (time 0) were taken at -15, 0, 15, 30, 45, 60, 75, 90, and 120 min. The prolactin and growth hormone responses were assessed. After ghrelin administration (cycles 2 and 4), plasma ghrelin, serum prolactin, and growth hormone levels increased rapidly, peaking at 15-30 min (p<0.001). The injection of thyrotropin-releasing hormone (cycle 3) stimulated prolactin secretion markedly (p<0.001), but reduced growth hormone levels significantly (p<0.05). Ghrelin induced a smaller prolactin increase than thyrotropin-releasing hormone (p<0.05). The combination of ghrelin and thyrotropin-releasing hormone induced a similar increase in prolactin levels as with thyrotropin-releasing hormone alone. No changes in growth hormone and prolactin levels were seen after saline injection. These results demonstrate that the stimulating effect of ghrelin on prolactin secretion is not additive with that of thyrotropin-releasing hormone.

The Effects of Novel and Newly Approved Antipsychotics on Serum Prolactin Levels: A Comprehensive Review

“…Veselinović et al [49] showed that estrogen treatment in healthy volunteers sensitizes women for PRL-elevating properties of antipsychotic medication. It is also known that ghrelin, a peptide hormone involved in metabolic homeostasis, stimulates PRL secretion, most probably by a direct action on the pituitary somatomammotroph cells (progenitor cells of lactotroph cells that can produce both PRL and growth hormone) [50–52]. A relatively large body of evidence has shown that tachykinins can modify the secretion of PRL in a rather complex fashion, having a stimulatory effect at the pituitary level, but in some circumstances (via modulating hypothalamic dopamine release) also an inhibitory one [4].…”

The Relationship of Appetitive, Reproductive and Posterior Pituitary Hormones to Alcoholism and Craving in Humans

“…Lactotrope function is primarily regulated by thyrotropin-releasing hormone (TRH) which facilitates, and dopamine which inhibits, the synthesis and secretion of prolactin. There is also preliminary evidence that ghrelin stimulates prolactin secretion in healthy women, but the effect is less than TRH and is not additive to TRH (Messini et al 2010a). Prolactin also decreases lutienizing (LH) and follicle stimulating hormone (FSH) secretion that accounts for the lack of fertility and changes in the menstrual cycle associated with hyperprolactinemia (Murphy et al 2006).…”

Prolactin concentrations in newly diagnosed, antipsychotic-naïve patients with nonaffective psychosis

“…In contrast to other pituitary hormones that are largely controlled by releasing factors, prolactin secretion is controlled mainly by an inhibiting factor, dopamine (Engler et al, 2009). However, prolactin is also partially regulated by thyrotropin-releasing hormone (TRH) through a extracellular signal-regulated kinase (Oride et al, 2009) and ghrelin, a peptide hormone involved in metabolic homeostasis, (Messini et al, 2010) which stimulates prolactin secretion by a direct action on the pituitary somatomammotroph cells. Prolactin release is also activated during the stress response (Jaroenporn et al, 2007).…”