The duration of prolactin secretory bursts from the pituitary is independent from both prolactin and gonadal steroid plasma levels in women and in men

Abstract

The intrinsic secretory characteristics of prolactin (PRL) have been investigated using newly developed algorhythms for instantaneous secretory rate (ISR) computation. PRL secretory rate, its intrinsic pulsatile characteristics and their possible dependance from gonadal steroids were investigated in five groups of subjects: a) 11 women during the follicular and luteal phase of the same menstrual cycle; b) 5 healthy postmenopausal women; c) 6 women affected by functional hyperprolactinemia; d) 5 normal men; e) 4 agonadal subjects before and during testosterone replacement therapy. All subjects underwent a 6 hours pulsatility study, from 08:00 to 14:00, sampling every 10 minutes. PRL plasma concentrations were determined using a RIA system and the presence of PRL secretory pulses was evaluated with program DETECT, both on plasma time series and after ISR computation. A distinct PRL episodic release was observed in all groups (follicular phase: 5.5 +/- 0.5, luteal phase: 6.5 +/- 0.6, postmenopause: 5 +/- 1, hyperprolactinemic women: 4.2 +/- 0.8, men: 4.8 +/- 0.4, agonadal before testosterone: 6 +/- 1, agonadal during testosterone administration: 5.3 +/- 0.3 peaks/6h), but mainly the computation of ISR allowed to demonstrate that the duration of the lactotropes secretory events was constant in all groups studied. PRL secretory bursts duration ranged between 23.1 +/- 1.8 and 25.4 +/- 2.5 minutes independently both on PRL or on sex steroid plasma levels. In conclusion, the present report shows that in different physiological conditions the intrinsic secretory bursts from lactotropes are constant in duration independently from the functional state, sex and the steroid hormone levels.

Prolactin Secretion in Healthy Adults Is Determined by Gender, Age and Body Mass Index

“…However the role of estrogens in regulating PRL secretion is certainly not straightforward. During the menstrual cycle no influence of different estradiol concentrations on PRL is demonstrable, but in this study only part of the 24 h cycle was analyzed [32]. Furthermore, the PRL increase after TRH injection is independent of the stage of the menstrual cycle [33].…”

Sexual dysfunction in males with chronic hepatitis C and antiviral therapy: interferon-induced functional androgen deficiency or depression?

“…In our study, mean serum prolactin levels were significantly increased during interferon therapy. As it has been demonstrated that the duration and frequency of prolactin secretory bursts from the pituitary are independent from gonadal steroid plasma levels in women and in men (Genazzani et al 1994), we assume that the observed increase in mean serum prolactin values is not secondary to alterations in gonadal steroid concentrations. Rather we may speculate that interferon therapy either directly affected lactotrope cells in the pituitary, or hypothalamic factors which control prolactin secretion, or both.…”

Experimental hyperprolactinemia in a rat model: alteration in centrally mediated neuroerectile mechanisms

“…But Genazzani and associates have shown that the duration of prolactin burst from the pituitary is independent from both prolactin and gonadal steroidal hormones. 53 As the LH and FSH response to exogenous GnRH is frequently normal or frankly excessive in these patients suggesting a normal pituitary gonadotrophin reserve, the defect is likely to reside in the hypothalamus and is generally thought to be a functional and potentially reversible alteration in GnRH secretion. 54 Severe hyperprolactinemia (prolactin b 2000 mUal) may cause hypogonadism and is almost invariably associated with sexual dysfunction in the male.…”