Anderson, Richard A.

SummaryBackgroundGonadotropin‐inhibitory hormone (GnIH, human homologue of RFRP‐3) suppresses gonadotropin secretion in animal models, but its effects have not been studied in the human.ObjectiveWe tested the hypotheses that exogenous GnIH inhibits LH secretion (i) in postmenopausal women and (ii) in men concurrently administered exogenous kisspeptin.DesignFollowing in vitro and in vivo preclinical studies to functionally characterize the GnIH peptide, a dose‐finding study (human GnIH: 1·5–150 μg/kg/h, iv for 3 h) was undertaken, and 50 μg/kg/h selected for further evaluation. Five postmenopausal women were administered 50 μg/kg/h iv infusion for 3 h or vehicle on two separate days. Four men were administered kisspeptin‐10 (0·3 μg/kg iv bolus) with simultaneous infusion of GnIH (50 μg/kg/h, iv for 3 h) or vehicle.ParticipantsHealthy postmenopausal women (mean age 58 ± 2 years, LH: 30·8 ± 2·9 IU/l, FSH: 78·7 ± 6·4 IU/l, oestradiol: <50 pmol/l) and men (39·8 ± 2·1 years, mean total testosterone 12·1 ± 1·8 nmol/l, LH 2·2 ± 0·2 IU/l).Primary outcomeChange in area under curve (AUC) of LH during GnIHvs vehicle.ResultsDuring GnIH administration in postmenopausal women, LH secretion decreased (ΔAUC: −9·9 ± 1·8 IU/3 h) vs vehicle (ΔAUC: −0·5 ± 1·7 IU/3 h; P = 0·02). Kisspeptin‐10‐stimulated LH responses in men were not affected by GnIH co‐administration (60‐min AUC of LH 6·2 ± 0·8 IU/h with kisspeptin‐10 alone, 6·3 ± 1·0 IU/h, kisspeptin‐10 with GnIH, P = 0·72). Exogenous GnIH was well tolerated, with no adverse events reported.ConclusionsGonadotropin‐inhibitory hormone decreased LH secretion in postmenopausal women in this first‐in‐human study. Kisspeptin‐stimulated LH secretion in men was not inhibited during concomitant administration of GnIH.

Context: Kisspeptin and neurokinin B (NKB) are obligate for normal gonadotropin secretion, but their hierarchy is unexplored in normal women. Objective: To investigate the interaction between kisspeptin and NKB on estrogen-regulated LH secretion. Design: Women were treated with neurokinin-3 receptor (NK3R) antagonist followed by transdermal estradiol to induce LH secretion 48 hours later, with kisspeptin-10 or vehicle infusion during estrogen administration in a 2-way crossover study. Setting: Clinical research facility. Patients or other participants: Healthy females with regular menses. Intervention(s): NK3R antagonist AZD4901 40 mg twice daily orally was taken from cycle day 4–6 for 6 days (n = 10, with 10 no treatment controls). Transdermal estradiol patches (200 μg/d) were applied after 5 days of NK3R antagonist treatment. At 24-hour estradiol treatment, women were randomized to 7-hour kisspeptin-10 (4 μg/kg/h) or vehicle iv infusion, with the alternate infusion in a subsequent cycle. Main outcome measure(s): Plasma gonadotropin and estradiol secretion. Results: After an initial suppression, LH secretion was increased 48 hours after estradiol treatment. Kisspeptin-10 increased LH secretion during the inhibitory phase, and LH remained elevated beyond the discontinuation of kisspeptin-10 infusion. NK3R antagonist decreased LH pulse frequency (0.5 ± 0.2 vs 0.7 ± 0.2 pulses/h, P &lt; .05) and stimulated FSH response to kisspeptin-10 infusion (10.7 ± 11.0 vs 5.0 ± 3.6 IU/L, P &lt; .05) with a nonsignificant rise in LH. The duration of LH response was blunted, with LH being lower at 48 hours (7.5 ± 4.8 vs 15.0 ± 11.4 IU/L, P &lt; .05). Conclusions: These data demonstrate that NKB signaling regulates GnRH/LH secretion in normal women, and is predominantly proximal to kisspeptin in mediating estrogenic positive and negative feedback on LH secretion.

Context: Polycystic ovary syndrome (PCOS), the most common endocrinopathy in women, is characterized by high secretion levels of LH and T. Currently, there is no treatment licensed specifically for PCOS. Objective: The objective of this study was to investigate whether a targeted therapy would decrease LH pulse frequency in women with PCOS, subsequently reducing serum LH and T concentrations and thereby presenting a novel therapeutic approach to the management of PCOS. Design: This study is a double-blind, double-dummy, placebo-controlled, phase 2 trial. Settings: University hospitals and private clinical research centers were included. Participants: Women with PCOS aged 18–45 years participated. Intervention: Intervention included AZD4901 (a specific neurokinin-3 [NK3] receptor antagonist) at a dose of 20, 40, or 80 mg/day or matching placebo for 28 days. Main Outcome Measure: Change from baseline in the area under the LH serum concentration–time curve over 8 hours (area under the curve) on day 7 relative to placebo was measured. Results: Of a total 67 randomized patients, 65 were evaluable. On day 7, the following baseline-adjusted changes relative to placebo were observed in patients receiving AZD4901 80 mg/day: 1) a reduction of 52.0% (95% confidence interval [CI], 29.6–67.3%) in LH area under the curve; 2) a reduction of 28.7% (95% CI, 13.9–40.9%) in total T concentration; and 3) a reduction of 3.55 LH pulses/8 hours (95% CI, 2.0–5.1) (all nominal P &lt; .05). Conclusions: The NK3 receptor antagonist AZD4901 specifically reduced LH pulse frequency and subsequently serum LH and T concentrations, thus presenting NK3 receptor antagonism as a potential approach to treating the central neuroendocrine pathophysiology of PCOS.

AbstractRationaleLow serum testosterone is commonly observed in men with type 2 diabetes (T2DM), but the neuroendocrine pathophysiology remains to be elucidated.ObjectivesThe hypothalamic neuropeptide kisspeptin integrates metabolic signals with the reproductive axis in animal models. We hypothesized that administration of exogenous kisspeptin‐10 will restore luteinizing hormone (LH) and testosterone secretion in hypotestosteronaemic men with T2DM.ParticipantsFive hypotestosteronaemic men with T2DM (age 33·6 ± 3 years, BMI 40·6 ± 6·3, total testosterone 8·5 ± 1·0 nmol/l, LH 4·7 ± 0·7 IU/l, HbA1c 7·4±2%, duration of diabetes <5 years) and seven age‐matched healthy men.Experiment 1Mean LH increased in response to intravenous administration of kisspeptin‐10 (0·3 mcg/kg bolus) both in healthy men (5·5 ± 0·8 to 13·9 ± 1·7 IU/l P < 0·001) and in men with T2DM (4·7 ± 0·7 to 10·7 ± 1·2 IU/l P = 0·02) with comparable ΔLH (P = 0·18).Experiment 2Baseline 10‐min serum sampling for LH and hourly testosterone measurements were performed in four T2DM men over 12 h. An intravenous infusion of kisspeptin‐10 (4 mcg/kg/h) was administered for 11 h, 5 days later. There were increases in LH (3·9 ± 0·1 IU/l to 20·7 ± 1·1 IU/l P = 0·03) and testosterone (8·5 ± 1·0 to 11·4 ± 0·9 nmol/l, P = 0·002). LH pulse frequency increased from 0·6 ± 0·1 to 0·9 ± 0 pulses/h (P = 0·05) and pulsatile component of LH secretion from 32·1 ± 8·0 IU/l to 140·2 ± 23·0 IU/l (P = 0·007).ConclusionsKisspeptin‐10 administration increased LH pulse frequency and LH secretion in hypotestosteronaemic men with T2DM in this proof‐of‐concept study, with associated increases in serum testosterone. These data suggest a potential novel therapeutic role for kisspeptin agonists in enhancing endogenous testosterone secretion in men with T2DM and central hypogonadism.