Sandra Valenti

A cross-over study with the two novel dopaminergic drugs cabergoline and quinagolide in hyperprolactinemic patients

Cabergoline and quinagolide, two new dopamine agonist drugs with long-lasting activity, are currently under investigation for the treatment of hyperprolactinemia. At present, studies comparing these drugs for tolerability and efficacy in the same patients are lacking. It was our aim to make such a comparison in an open randomized cross-over trial. Cabergoline (0.5 mg twice weekly) and quinagolide (75 µg once daily) were given orally. Each drug was administered for 12 weeks. Treatment with the second drug was started after the recurrence of hyperprolactinemia. Twelve women with hyperprolactinemia due to idiopathic disease (n=6), microprolactinoma (n=5) or postsurgical empty sella (n=1) were evaluated. Six women were amenorrheic and 6 were oligomenorrheic. Ten had spontaneous or provoked galactorrhea. Baseline characteristics (age, clinical signs and PRL levels) of patients initially allocated to the two treatment groups were similar. Nine patients completed both treatment cycles and PRL levels were lower under cabergoline (10.7±3.7 µg/L) than under quinagolide (25.0±7.7 µg/L; p<0.05). One patient discontinued cabergoline because of dryness of the eyes after having completed the quinagolide cycle and 2 patients initially treated with cabergoline discontinued quinagolide because of gastrointestinal symptoms. After completion of the first treatment cycle, the time of recurrence of hyperprolactinemia was significantly longer after cabergoline (14±7 weeks) than after quinagolide (5±1 weeks; p<0.05). At week 12, normal PRL levels (<20 µg/L) were observed in 10 and 6 women during cabergoline and quinagolide, respectively. Only one case was resistant to both drugs. The clinical effects of the two treatments were similar. At week 12, minor side effects were described in 5 and 9 women on cabergoline and quinagolide. The number of patients without side effects was significantly higher after cabergoline (n=6) than after quinagolide (n=1; p<0.01). Our study indicates that, at the doses employed, cabergoline shows a better long-lasting efficacy and tolerability than quinagolide. Drop-outs due to severe side effects occurred with both drugs. However, quinagolide could be regarded as a further choice in the medical management of hyperprolactinemia.

Nitric oxide modulates in vivo and in vitro growth hormone release in acromegaly.

Nitric oxide (NO) has recently been shown to modulate pituitary secretion both in vivo and in vitro. The aim of this study was to investigate the effects of this chemical transmitter on spontaneous and growth-hormone-releasing hormone (GHRH)-induced growth hormone (GH) secretion in acromegalic patients, as well as from GH-secreting tumors maintained in vitro. The study was carried out in 7 acromegalic patients (46.2 +/- 2 years) and in 5 normal subjects (40.1 +/- 1.5 years). GH and prolactin (PRL) secretion were assayed during the administration of isosorbide dinitrate (ID, 5 mg, orally), an NO donor, GHRH, and ID plus GHRH. During ID, a significant (p < 0.05) increase (37%) over basal GH levels was only observed in acromegalics. There was no change in GH levels in response to GHRH or ID plus GHRH in either group. No significant change in PRL levels was observed in either group during ID, while GHRH, with or without ID, induced a slight increase in PRL levels in acromegalics only. Tumor specimens were obtained by selective transsphenoidal adenomectomy, and the cells were plated and incubated for 1, 2 and 24 h in the presence of sodium nitroprusside, a releaser of NO (SNP, 0.3 or 0.6 mM), of GHRH (10-8 M) or of both. SNP significantly (p < 0.001) increased GH levels in a dose-dependent manner (R = 0.99, p = 0.02), but was unable to modify the GH response to GHRH. In acromegalics, a significant correlation (R = 0.822, p < 0.045) and a correlation near the limit of significance (R = 0.73, NS) were observed respectively between the in vivo GH response to ID and the in vitro response to SNP at 24 h. No significant effect was observed on PRL secretion during SNP incubations, while GHRH produced a significant increase in PRL after 2 and 24 h incubation in acromegalics. These observations indicate that NO plays a stimulatory role in vivo and in vitro on GH secretion in acromegalic patients.

Circulating nitric oxide is modulated by recombinant human TSH administration during monitoring of thyroid cancer remnant

During the administration of recombinant human TSH (rhTSH) to monitor differentiated thyroid carcinoma, mild side effects, such as nausea and headaches, often occur. The origin of these is not clear. Since changes in TSH and thyroid hormones can modulate some endothelial-derived factors, we aimed at testing whether rhTSH administration induces changes in nitric oxide. We studied 25 patients (56.6±12.6 yr) who had undergone thyroidectomy followed by ablative radioiodine for papillary thyroid cancer and who were under follow-up. While L-thyroxine therapy continued, thyroglobulin (Tg), TSH, free-T3, free-T4 and nitrite-plus-nitrate (NOx) concentrations were evaluated before and after rhTSH administration (0.9 mg im on 2 consecutive days). Mean TSH showed a huge increase from baseline (0.1±0.0 mIU/l) to day 3 (216.3±17.5 mIU/l, p>0.001), which was not accompanied by changes in thyroid hormones. Mean baseline NOx levels were 12.6±1.2 µmoles/l and showed a significant increase on day 3 (20.1±1.2 µmoles/l, p>0.05 vs day 0), followed by progressive reduction from day 6 (18.1±2.8 µmoles/l) to day 9 (10.6±1.3 µmoles/l, p>0.05 vs day 0). There was a significant (p=0.04) correlation between the percentage increase in TSH and the percentage increase in NOx. On the other hand, increase in TSH did not correlate with the percentage decrease in NOx from day 6 to day 9. No correlation was noted between the increase in TSH or NOx and the occurrence or severity of the symptoms. Our study shows that, during rhTSH testing, circulating nitric oxide increases. This endothelial-derived factor might, in turn, mediate the occurrence of vasomotor headache and nausea in some particularly susceptible patients.

Melatonin Participates in the Control of Testosterone Secretion from Rat Testis

Abstract: The androgen milieu plays an important role in the control of immunity, and melatonin (MLT) is known to modulate the immune response as well. Our recent studies have focused on the role of MLT in controlling androgen secretion from rat testis. The presence of MLT receptors, their modulation, and the effect of MLT on steroidogenesis have been studied on Percoll‐purified rat Leydig cells (LCs) cultured in vitro. MLT receptors present in adult rat LCs (Bmax= 46.7 ± 3.5 fmol/mg protein; Kd= 88.7 ± 6.2 pmol/l) are coupled through a pertussis toxin‐sensitive G‐protein and are downregulated by prolonged exposure to MLT itself. When acutely added for three hours, MLT (0.4‐400 nM) inhibits T secretion in response to LH, forskolin, and GnRH, but sensitizes cAMP‐dependent T secretion when present in the preincubation media (16 h). The acute inhibition of adenylyl cyclase and the block of 17‐20‐desmolase (with increased 17‐OH‐progesterone) and of calcium release from the intracellular stores, followed by sensitization of the adenylyl cyclase activity in the long term, are described as mechanisms of MLT action. Ultimately, our studies suggest that MLT is likely to control the immune response not only through its direct effects, but also by finely modulating the androgen milieu.

Serum leptin levels in males with delayed puberty during short-term pulsatile GnRH administration

Leptin may be a possible trigger for puberty. In normal males, it has been shown that leptin increases from the pre-pubertal to the early pubertal stage, and then declines in the late pubertal stage. We examined leptin levels in six male adolescents (mean age 16.3±0.6 yr; range 14.2-17.6 yr) with delayed puberty (constitutional delay of puberty no.=2; idiopathic hypogonadotropic hypogonadism no.=4) during 120 days of subcutaneous pulsatile GnRH administration. A group of subjects in pre-puberty (no.=11), early-puberty (n=10) and mid-puberty (no.=7) were evaluated as controls. Morning blood samples were taken for determination of leptin, testosterone, LH and FSH levels. In delayed puberty subjects blood samples were taken every 30 days after the start of GnRH administration. At each examination BMI and testicular volume were evaluated. A follow-up examination was performed in the 6 patients 1.3-7.5 yr after the end of the 120 days of GnRH therapy. At baseline evaluation in delayed puberty mean leptin levels were 11.3±2.0 ώg/l (median 11.3 ώg/l; range 4.7-17.3 ώg/l) and were higher than those found in pre-puberty (p=0.04) and mid-puberty (p=0.001). During GnRH administration there was no change in BMI and leptin levels but there was an increase in gonadotrophin levels, testosterone and testicular volume. One undred and twenty days after, mean serum leptin were 10.1±2.1 ώg/l (median 9.1 ώg/l; range 3.4-16.8 ώg/l). At the end of the study, leptin levels were higher in delayed puberty than in mid-puberty (p=0.002). At the follow-up examination leptin levels were 4.3±1.3 ώg/l (median 3.4 ώg/l; range 1.4-9.1 ώg/l) (p=0.03 vs end of 120 days GnRH therapy) while testosterone and BMI were not changed. In conclusion 120-day pulsatile GnRH administration induced in males with delayed puberty physiological-like pubertal changes but not the decline in leptin levels reported during the progression of puberty. Therefore, in males with delayed puberty an impairment in the phenomenon of leptin decline associated with progression of puberty could be suggested. However after retrospective diagnosis of pubertal delay and long-term therapy in subjects with idiopathic hypogonadotropic hypogonadism leptin levels declined. These data seem to indicate that time more than increase in testosterone levels and testicular volume is the determinant of leptin decline at puberty.

Delayed puberty in uremia: Pituitary-gonadal function during short-term pulsatile luteinizing hormone-releasing hormone administration

Pubertal development is frequently delayed or disordered in children with chronic renal failure. Both neuroendocrine and peripheral alterations due to uremia have been hypothesized to explain the impairment in the pituitary gonadal axis. The aim of the present study was to evaluate quantitative (immunological) and qualitative (biological) LH secretion, as well as FSH and sex steroids, before and during 7 days of sc LHRH administration (136–150 ng/kg bw every 120 min) in 5 uremic children (13.1–14.8 yr) with delayed puberty. Six nonuremic children (13.2–17.8 yr) with delayed puberty underwent the same schedule and served as control group. On day 0 mean immunoreactive LH (l-LH) levels were higher in uremic (4.5±0.9 mlU/ml) than in nonuremic (1.9±03 mlU/ml; p<0.05) subjects while no differences were observed in bioactive LH (B-LH) levels (2.9±0.7 mlU/ml vs 2.4±0.3 mlU/ml). In both groups of subjects testosterone was at prepubertal levels. Spontaneous l-LH and B-LH pulses were observed sporadically in both uremic and nonuremic subjects. Short-term pulsatile LHRH ad-ministration induced significant increases in B-LH, I-LH, FSH and testosterone. The B/l LH ratio increased from day 0 (0.7±0.2) to day 7 (1.310.4; p<0.05) in uremics while it showed wide fluctuations in nonuremic subjects. On day 7, 4 uremic and 5 nonuremic subjects showed a pulsatile release of B-LH after exogenous LHRH pulses. Our data document that in uremia there are qualitative as well as quantitative abnormalities in pituitary gonadal secretion. Seven days of pulsatile LHRH administration seems to partially reverse the impaired activity of the pituitary gonadal axis. Uremic and nonuremic subjects showed the same responsiveness to the LHRH administration. A disturbed endogenous LHRH discharge could be hypothesized in delayed or disordered puberty in uremic children, as has already been suggested in nonuremic children with delayed puberty.

The effect of non-steroidal antiandrogen flutamide on luteinizing hormone pulsatile secretion in male-to-female transsexual subjects.

We evaluated LH pulsatile patterns before and 4 weeks after the oral administration of flutamide (750 mg/day) in 9 male-to-female transsexuals (age range 17–28 yr) requesting gender reassignment. Flutamide was given to explore the feedback role of androgens on the LHRH-LH unit in LH pulsatility in transsexuals. Seven normal agematched men served as a control group, without receiving flutamide, due to ethical considerations. LH pulsatility was evaluated on samples collected every 15 min for 360 min. FSH, PRL, cortisol, SHBG and sex steroids were evaluated on pooled samples. LH pulses were analyzed by the Santen and Bardin algorithm, slightly modified. No differences in FSH, PRL, total- or free-testosterone, estradiol and SHBG levels were noted between transsexuals and controls. Normal circadian Cortisol decline was observed in all subjects. Mean LH levels (p<0.05) and LH pulses (p<0.01) were significantly lower in transsexuals. Flutamide induced an increase in mean LH and testosterone levels (p<0.01). After flutamide administration there was an increase in LH pulse frequency (p<0.01) and the frequency and amplitude of LH pulses in transsexuals were restored to levels observed in controls. No differences in FSH, PRL or estradiol levels were found after flutamide. These data suggest that a decrease in LH pulse frequency could be an endocrine marker in male-to-female transsexuals. An increase in endogenous androgen negative feed-back could be speculated in these subjects. However, normal testosterone levels indirectly suggest that a normal qualitative LH secretion is maintained. Other factors in reducing LH pulse frequency and mean LH levels could be hypothesized. Nevertheless, flutamide, which provokes an in vivo blockade of endogenous androgen negative feed-back, is able to normalize impaired LH pulsatility in male-to-female transsexuals.

Effect of cholinergic tone on growth hormone-releasing hormone-induced secretion of growth hormone in normal aging

Aging is associated with an impairment in the GH response to GHRH and to several other stimuli of GH secretion. We evaluated the effect of pyridostigmine (PD) or placebo pretreatment (Protocol A: placebo or 120 mg PD orally at 8 a.m.; Protocol B: placebo or 60 mg PD twice orally at 9 p.m. and 7 a.m.) on GH responsiveness to GHRH (1 μg/kg BW bolus i.v. at 9 a.m.) in 15 normal elderly males (65–92 years) and in 14 normal young adults (20–37 years). GH response to GHRH was significantly reduced in elderly subjects compared to young adults (p <0.05). PD (Protocol A) increased GH release in both elderly and young subjects. In elderly men, PD enhanced GH response to GHRH. The phenomenon was more evident when PD was administered according to Protocol B (p <0.01). The area under the curve of GH was significantly greater after PD plus GHRH than it was after placebo plus GHRH (p <0.01). In young adults, PD induced an increase in GH responsiveness to GHRH when administered according to Protocol A (p <0.05) but not Protocol B. Both GH peak and AUC of GH after PD plus GHRH (Protocols A and B) in elderly subjects were not significantly different from the same parameters found in young subjects after placebo plus GHRH. Our data confirm that pituitary somatotrophin responsiveness to GHRH in man changes with aging. PD restores GH responsiveness to GHRH in elderly subjects. The effect of PD on GH secretion suggests that cholinergic mechanisms may be involved in GH control in normal aging. The study indicates that during the life span cholinergic neurons exert differential effects on GH control and/or that the neurohormonal pathway (somatostatin), which is the target of cholinergic tonus, acts differentially between night and morning. (Aging Clin. Exp. Res. 4: 231–237, 1992)

Circulating nitric oxide levels increase after anti-androgen treatment in male-to-female transsexuals.

Circulating nitric oxide is produced by the vascular endothelium under the influence of the sex steroid milieu and shows gender difference. Since data on hormonal manipulation in males are scant, the present study was designed to evaluate nitric oxide levels before and after anti-androgen treatment in young male-to-female (MF) transsexuals. Fifteen MF transsexuals aged 23.7±1.3 yr, with normal testicular volume and normal body mass index were studied. Twenty adult males aged 28.2±2.4 yr served as controls. A low nitrate diet was administered to all subjects throughout the study, starting 15 days before the beginning. Blood samples were drawn from all subjects on day 0; flutamide 750 mg/day was then administered to transsexuals for 30 days, and another sample was taken on day 30. In all subjects the concentration of nitrite plus nitrate (NOx), two stable compounds into which nitric oxide spontaneously decomposes, was determined; also total testosterone (T) and free testosterone (fT), 17βestradiol (E2), SHBG, δ4-androstenedione (A), DHEAS, 17-hydroxy-progesterone (OHP), LH, FSH and PRL were assayed. All hormones determined in controls and transsexuals were comparable at the beginning of the study. NOx was also comparable in controls (11.0±1.0 μM/l) and transsexuals (11.1±1.2 μM/l) and did not significantly correlate with any of the hormones assayed. After 30 days of flutamide administration, LH, T, fT, A and E2 increased; DHEAS decreased, while FSH, SHBG and PRL were unchanged; NOx rose significantly (18.7±1.7 μM/l; p<0.05), and its percentage increase with respect to pre-treatment levels correlated with that of E2 (R=0.77; p<0.01). Healthy males and MF transsexuals do not differ in terms of sex hormones and NOx levels. In neither group is NOx significantly correlated to any sex hormone assayed. Treatment with flutamide in MF transsexuals elicits an increase in androgens, which are not biologically active because of the androgen receptor blockade, and an increase in the estrogenic milieu, which correlates with the increase in NOx.

Prolactin decrease and shift to a normal-like isoform profile during treatment with quinagolide in a patient affected by an invasive prolactinoma.

Prolactin (PRL) circulates as multiple molecular weight variants: glycosylated phosphory lated, deamidated and sulphated forms. The profiles of the forms, as determined by isoelectrofocusing (IEF), differ in physiological and pathological conditions. The case of a 72-year-old woman affected by an invasive prolactinoma is described. The patient had undergone surgical treatment followed by radiotherapy at the age of 71 years. Bromocriptine therapy followed (up to 10 mg/die), but the PRL levels were still extremely high (over 13,000 µg/l as determined by IRMA, after dilution). We therefore treated the patient with quinagolide, at increasing dosages, from 150 µg/die on day 0 to 600 µg/die on day 220. This treatment progressively lowered PRL to 23.2 µg/l. In addition to a decrease in PRL levels, a progressive change in the IEF profile was also noted. Indeed, on day 0, the PRL isoforms were very acidic and during treatment they progres sively shifted toward a more basic range. For purpose of comparison PRL profiles were also determined in 8 women with pathological hyperprolactinaemia (group A, aged 16–50 years, PRL levels: 25.1–170.4 µg/l), in 6 normal women (group B, aged 25–29 years, PRL levels: 3.4–7.9 µg/l) and in 5 normal women during a TRH test (group C, aged 17–52 years, PRL levels: 2.7–10.3 µg/l). The profiles observed in group A had a single major peak at isoelectric point (pl) 6.5, while the group B and C profiles were more heterogeneous displaying multiple minor peaks, the majority of the molecules being in a more basic range (pi 6.9 for group B and pl 7.5 for group C). During treatment, the profiles of our subject at first resembled those of group A; subsequently, when the PRL levels had normalised, the profile resembled those noted in group B. Altered (immature?, more glycosilated?, less bioactive?) PRL molecules could be secreted by the tumour. These data show that quinagolide successfully reduced PRL levels, while inducing secretion of forms more similar to those found in women affected by pathological hyperprolactinaemia or in normal women.