Follicular and endocrine dose responses according to anti-Müllerian hormone levels in IVF patients treated with a novel human recombinant FSH (FE 999049)

The pregnancy outcomes among women receiving individualized algorithm dosing with follitropin delta: a systematic review of randomized controlled trials

PURPOSE

To investigate whether the ovarian stimulation with follitropin delta in an individualized algorithm-based manner is inferior to recombinant human-follicle stimulating's follitropin alfa or follitropin beta conventional dosing regarding a series of established primary endpoints.

METHODS

We conducted a registered systematic review (CRD42024512792) on PubMed-MEDLINE, Web of Science™, Cochrane Database of Systematic Reviews, and Scopus. Our search was designed to cover all relevant literature, particularly randomized controlled trials. We critically and comparatively analyzed the outcomes for each primary endpoint based on the intervention, reflected by the positive βhCG test, clinical pregnancy, vital pregnancy, ongoing pregnancy, live birth, live birth at 4 weeks, and multiple pregnancies.

RESULTS

Six randomized controlled trials were included in the quality assessment as priority manuscripts, revealing an 83.3% low risk of bias. Follitropin delta led to non-significant differences in each parameter of interest from positive βhCG test (691; 53.44% vs. 602; 46.55%), ongoing pregnancies (603; 53.79% vs. 518; 46.20%), clinical and vital pregnancies (1,073; 52.80% vs. 959; 47.19%), to live birth and at 4 weeks (595; 54.14% vs. 504; 45.85%) with only 2 losses, and even multiple pregnancies (8; 66.66% vs. 4; 33.33%). However, follitropin delta was well-tolerated among hypo- and hyper-responders without significant risk of ovarian hyperstimulation syndrome and/or preventive interventions in contrast with follitropin alfa or follitropin beta.

CONCLUSION

The personalized individualized-based algorithm dosing with follitropin delta is non-inferior to conventional follitropin alfa or follitropin beta. It is as effective in promoting a similar response in women without significant comparable adverse effects.

Follitropin delta combined with menotropin in patients at risk for poor ovarian response during in vitro fertilization cycles: a prospective controlled clinical study

BACKGROUND

The maximum daily dose of follitropin delta for ovarian stimulation in the first in vitro fertilization cycle is 12 μg (180 IU), according to the algorithm developed by the manufacturer, and based on patient's ovarian reserve and weight. This study aimed to assess whether 150 IU of menotropin combined with follitropin delta improves the response to stimulation in women with serum antimullerian hormone levels less than 2.1 ng/mL.

METHODS

This study involved a prospective intervention group of 44 women who received 12 μg of follitropin delta combined with 150 IU of menotropin from the beginning of stimulation and a retrospective control group of 297 women who received 12 μg of follitropin delta alone during the phase 3 study of this drug. The inclusion and exclusion criteria and other treatment and follow-up protocols in the two groups were similar. The pituitary suppression was achieved by administering a gonadotropin-releasing hormone (GnRH) antagonist. Ovulation triggering with human chorionic gonadotropin or GnRH agonist and the option of transferring fresh embryos or using freeze-all strategy were made according to the risk of developing ovarian hyperstimulation syndrome.

RESULTS

Women who received follitropin delta combined with menotropin had higher estradiol levels on trigger day (2150 pg/mL vs. 1373 pg/mL, p < 0.001), more blastocysts (3.1 vs. 2.4, p = 0.003) and more top-quality blastocysts (1.8 vs. 1.3, p = 0.017). No difference was observed in pregnancy, implantation, miscarriage, and live birth rates after the first embryo transfer. The incidence of ovarian hyperstimulation syndrome did not differ between the groups. However, preventive measures for the syndrome were more frequent in the group using both drugs than in the control group (13.6% vs. 0.6%, p < 0.001).

CONCLUSIONS

In women with serum antimullerian hormone levels less than 2.1 ng/mL, the administration of 150 IU of menotropin combined with 12 μg of follitropin delta improved the ovarian response, making it a valid therapeutic option in situations where ovulation triggering with a GnRH agonist and freeze-all embryos strategy can be used routinely.

TRIAL REGISTRATION

U1111-1247-3260 (Brazilian Register of Clinical Trials, available at https://ensaiosclinicos.gov.br/rg/RBR-2kmyfm ).

A Narrative Review Discussing the Efficiency of Personalized Dosing Algorithm of Follitropin Delta for Ovarian Stimulation and the Reproductive and Clinical Outcomes

Background: Follitropin delta is the third recombinant human follicle-stimulating hormone (r-hFSH) expressed in a host cell line of human fetal retinal origin that currently emphasizes that the actual tendency of administration is a personalized dosing algorithm based on the anti-Müllerian hormone (AMH) and body mass index (BMI) for ovarian stimulation. Methods: In this context, we aimed, in the present manuscript, to gather all available data published between 2018-2022 regarding the co-administration and administration of follitropin delta and the clinical outcomes reported following an in vitro fertilization (IVF). Results: Follitropin delta is non-inferior in contrast to its previously launched agents for ovarian stimulation, enhancing a similar-to-superior response reflected by both the reproductive and pregnancy outcomes in parallel with a low risk of ovarian hyperstimulation syndrome (OHSS), being well tolerated. The body weight and AMH level are factors that may influence the outcome in a patient. Despite controversy and results that refute these arguments on several occasions, follitropin delta exceeds the benefits of conventional dosing with either follitropin alfa or follitropin beta. Thus, all post hoc, derived analyses and subsets of patients that participated in subsequent studies support this statement. Conclusions: Despite the relatively limited spectrum of data in the current literature, most authors brought potent proof, supporting the subsequent use of this drug depending on the patient's profile and overcoming ethnic-related limitations. Although others contradict these observations, this topic and drug possess substantial potential, which is why additional studies are mandatory to fill the existing gaps in our knowledge and expand these experiences at a larger scale supported by the obtained reproductive and clinical outcomes that clearly indicate an overcoming of all limitations.

Pharmacokinetics and Safety of Follitropin Delta in Gonadotropin Down-Regulated Healthy Chinese Women

BACKGROUND

Follitropin delta, a novel recombinant follicle-stimulating hormone (rFSH) preparation derived from a human cell line, has different pharmacokinetic and pharmacodynamic properties compared with existing rFSH preparations expressed by Chinese hamster ovary cells (CHO).

OBJECTIVES

The objective of this study was to assess the pharmacokinetic characteristics, dose proportionality, and safety of follitropin delta in healthy Chinese women.

METHODS

This was a phase I, randomized, open-label study. Twenty-four healthy Chinese women were randomized (1:1:1) to receive a single subcutaneous administration of follitropin delta 12, 18, or 24 μg. The pharmacokinetic parameters (maximum observed serum concentration [C_max], time to reach C_max [t_max], area under the serum concentration-time curve from dosing to infinity [AUC_∞], and elimination phase half-life [t_½]) of follitropin delta were derived using noncompartmental analysis.

RESULTS

Following a single subcutaneous administration of follitropin delta 12, 18, or 24 μg, mean C_max (0.388, 0.677, and 0.825 ng/mL, respectively) and AUC_∞ (41.3, 62.9, and 83.1 h·ng/mL, respectively) increased in a dose-proportional manner. The median t_max was 24 h, and the mean t_½ was in the range of 50.5-60.9 h. All treatment-related adverse events were categorized as mild, except for one case of urticaria from the follitropin delta 18-μg dose group which was considered moderate. Only one woman presented with elevation of alanine transaminase and aspartate aminotransferase at the follow-up visit, which was reported as a treatment-emergent adverse event. There were no injection-site reactions and none of the participants showed any confirmed presence of treatment-induced anti-FSH antibodies.

CONCLUSIONS

The administration of single doses of follitropin delta to healthy Chinese women demonstrated dose-proportional pharmacokinetics over the dose range of 12-24 μg, and these doses were well tolerated.

CLINICAL TRIAL REGISTRATION

Clinicaltrials.gov registration no. NCT04150861.

Considerations when treating male pubertal delay pharmacologically

INTRODUCTION

Delayed puberty, defined as the appearance of pubertal signs after the age of 14 years in males, usually affects psychosocial well-being. Patients and their parents show concern about genital development and stature. The condition is transient in most of the patients; nonetheless, the opportunity should not be missed to diagnose an underlying illness.

AREAS COVERED

The aetiologies of pubertal delay in males and their specific pharmacological therapies are discussed in this review.

EXPERT OPINION

High-quality evidence addressing the best pharmacological therapy approach for each aetiology of delayed puberty in males is scarce, and most of the current practice is based on small case series or unpublished experience. Male teenagers seeking attention for pubertal delay most probably benefit from medical treatment to avoid psychosocial distress. While watchful waiting is appropriate in 12- to 14-year-old boys when constitutional delay of growth and puberty (CGDP) is suspected, hormone replacement should not be delayed beyond the age of 14 years in order to avoid impairing height potential and peak bone mass. When primary or central hypogonadism is diagnosed, hormone replacement should be proposed by the age of 12 years provided that a functional central hypogonadism has been ruled out. Testosterone replacement regimens have been used for decades and are fairly standardised. Aromatase inhibitors have arisen as an interesting alternative for boy with CDGP and short stature. Gonadotrophin therapy seems more physiological in patients with central hypogonadism, but its relative efficacy and most adequate timing still need to be established.

Prospective multicenter non-interventional real-world study to assess the patterns of use, effectiveness and safety of follitropin delta in routine clinical practice (the PROFILE study)

OBJECTIVE

To observe the real-world utilization patterns, effectiveness and safety profile of follitropin delta in women ≥18 years naïve to ovarian stimulation undergoing in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI).

DESIGN

Prospective, multinational, multicenter, observational study. All IVF/ICSI treatment protocols were conducted according to routine clinical practice, including undertaking fresh/frozen transfers. Outcomes included use of dosing algorithm, follitropin delta dosing patterns, ovarian response, pregnancy rates and adverse drug reactions (ADRs).

RESULTS

The first ovarian stimulation cycle using follitropin delta was initiated in 944 women. Mean baseline demographics were: age, 33.5 ± 4.7 years; bodyweight, 67.1 ± 13.6 kg; anti-Müllerian hormone, 20.3 ± 16.1 pmol/L (2.84 ± 2.25 ng/mL). The dosing algorithm was used to calculate the follitropin delta daily starting dose in 893/944 women (94.5%). The mean difference between the calculated and prescribed daily dose was small (0.2 ± 1.40 µg). The mean daily starting follitropin delta dose was 10.4 ± 2.72 µg and the mean total dose administered was 104 µg. Follitropin delta dose adjustments were reported for 57/944 (6.0%) women. The mean number of retrieved oocytes was 10.1 ± 7.03. Ongoing pregnancy at 10-11 weeks was reported for 255 women (27.0% per initiated cycle and 43.1% per fresh transfer [n=592]). Cumulative ongoing pregnancy rate after fresh and/or frozen transfer was 36.4% (344/944). Four women discontinued follitropin delta due to ADRs. Ovarian hyperstimulation syndrome (OHSS) was the most frequently reported ADR (n=37 [3.9%]); most cases of OHSS were of mild or moderate intensity (n=30 [3.2%]).

CONCLUSIONS

This large real-world study of follitropin delta utilization patterns confirms its good pregnancy rates while minimizing OHSS risk during first ovarian stimulation cycle.

Recent advancement in the treatment of boys and adolescents with hypogonadism

Clinical manifestations and the need for treatment varies according to age in males with hypogonadism. Early foetal-onset hypogonadism results in disorders of sex development (DSD) presenting with undervirilised genitalia whereas hypogonadism established later in foetal life presents with micropenis, cryptorchidism and/or micro-orchidism. After the period of neonatal activation of the gonadal axis has waned, the diagnosis of hypogonadism is challenging because androgen deficiency is not apparent until the age of puberty. Then, the differential diagnosis between constitutional delay of puberty and central hypogonadism may be difficult. During infancy and childhood, treatment is usually sought because of micropenis and/or cryptorchidism, whereas lack of pubertal development and relative short stature are the main complaints in teenagers. Testosterone therapy has been the standard, although off-label, in the vast majority of cases. However, more recently alternative therapies have been tested: aromatase inhibitors to induce the hypothalamic-pituitary-testicular axis in boys with constitutional delay of puberty and replacement with GnRH or gonadotrophins in those with central hypogonadism. Furthermore, follicle-stimulating hormone (FSH) priming prior to hCG or luteinizing hormone (LH) treatment seems effective to induce an enhanced testicular enlargement. Although the rationale for gonadotrophin or GnRH treatment is based on mimicking normal physiology, long-term results are still needed to assess their impact on adult fertility.

Randomized, assessor-blind, antimüllerian hormone-stratified, dose-response trial in Japanese in vitro fertilization/intracytoplasmic sperm injection patients undergoing controlled ovarian stimulation with follitropin delta

OBJECTIVE

To establish the relationship between follitropin delta doses (recombinant follicle-stimulating hormone produced from the human cell line PER.C6) and ovarian response in Japanese women undergoing in vitro fertilization/intracytoplasmic sperm injection treatment and to evaluate the influence of initial antimüllerian hormone (AMH) levels.

DESIGN

Randomized, controlled, assessor-blind, AMH-stratified (low 5.0-14.9 pmol/L; high 15.0-44.9 pmol/L) dose-response trial.

SETTING

Reproductive medicine clinics.

PATIENT(S)

A total of 158 Japanese women (20-39 years of age).

INTERVENTION(S)

Controlled ovarian stimulation with 6, 9, or 12 μg/d of follitropin delta or 150 IU/d follitropin beta as a reference arm in a gonadotropin-releasing hormone antagonist cycle.

MAIN OUTCOME MEASURE(S)

Number of oocytes retrieved.

RESULT(S)

Among all women who started stimulation, the mean number (± standard deviation) of oocytes retrieved in the 6 μg/d, 9 μg/d, and 12 μg/d follitropin delta groups was 7.0 ± 4.1, 9.1 ± 5.6, and 11.6 ± 5.6, respectively, and a significant dose-relation was established, which also remained significant within each AMH strata. Significant dose-responses also were observed for serum estradiol, inhibin A, and progesterone at end-of-stimulation with follitropin delta. The vital pregnancy rate per started cycle with follitropin delta was 19% for 6 μg/d, 20% for 9 μg/d, and 25% for 12 μg/d. The rate of early moderate/severe ovarian hyperstimulation syndrome with follitropin delta was 8% for 6 μg/d, 8% for 9 μg/d, and 13% for 12 μg/d, with 82% of the cases in the high AMH stratum.

CONCLUSION(S)

This trial establishes the dose-response relationship between follitropin delta and ovarian response in Japanese women.

CLINICAL TRIAL REGISTRATION NUMBER

NCT02309671.

A predictive formula for selecting individual FSH starting dose based on ovarian reserve markers in IVF/ICSI cycles

BACKGROUND

Although exogenous follicle-stimulating hormone (FSH) has been used for decades and millions of cycles have been performed worldwide until now, criteria for selecting the proper FSH starting dose have not been clearly identified. The aim of this study was to elaborate a formula based on markers of ovarian reserve for the calculation of the appropriate starting dose of FSH.

METHODS

A total of 931 patients underwent in vitro fertilization (IVF) treatment using long GnRH agonist protocol was retrospectively identified and reviewed. 673 cases of them with a normal ovarian response (4-14 retrieved oocytes) were used to analysis the predictive formula. All follicles 4-7 mm in diameter were counted in the same day of blood sample in both ovaries using transvaginal ultrasound scan. The modified protocol of each patient was recorded and analyzed in the same center. In another center were the numbers of retrieved oocytes of 750 validated patients recorded and analyzed.

RESULTS

A formula model based on age, AMH, and antral follicle count (AFC) was able to accurately predict the ovarian sensitivity and accounted for 57.2% of the variability of ovarian response to FSH. When tested in the same total population used to elaborate the model it predicts a high 46.88% rate of step-down protocol in higher-starting FSH dose group and about 57.92% of patients had their dose step-up modified in lower-starting FSH dose group during their treatment, respectively. And when tested in different population from another center used to elaborate the model it predicts a high 64.40% rate of ≥ 15 retrieved oocytes in higher-starting FSH dose group and about 22.50% of patients had ≤ 7 retrieved oocytes in lower-starting FSH dose group during their treatment, respectively.

CONCLUSIONS

In the present study we demonstrated that the individualized FSH starting dose may be calculated on the basis of a woman's age, AMH and AFC. The formula model might be a useful, immediate, and easily applicable tool for clinicians to predict the tailored starting dose of FSH during their daily clinical practice.

FSH Requirements for Follicle Growth During Controlled Ovarian Stimulation

Introduction: Ovarian follicle growth is a key step in the success of assisted reproductive treatment, but limited data exists to directly relate follicle growth to recombinant FSH (rFSH) dose. In this study, we aim to evaluate FSH requirements for follicular growth during controlled ovarian stimulation. Method: Single center retrospective cohort study of 1,034 IVF cycles conducted between January 2012-January 2016 at Hammersmith Hospital IVF unit, London, UK. Median follicle size after 5 days of stimulation with rFSH and the proportion of antral follicles recruited were analyzed in women treated with rFSH alone to induce follicular growth during IVF treatment. Results: Starting rFSH dose adjusted for body weight (iU/kg) predicted serum FSH level after 5 days of rFSH (r ² = 0.352, p < 0.0001), median follicle size after 5 days of rFSH, and the proportion of antral follicles recruited by the end of stimulation. Day 5 median follicle size predicted median follicle size on subsequent ultrasound scans (r ² = 0.58-0.62; p < 0.0001), and hence time to oocyte maturation trigger (r ² = 0.22, P < 0.0001). Insufficient rFSH starting dose that required >5% dose-increase was associated with increased variability in follicle size on the day of oocyte maturation trigger, and negatively impacted the number of mature oocytes retrieved. Conclusion: Weight-adjusted rFSH dose correlates with follicular growth during ovarian stimulation. Early recruitment of follicles using a sufficient dose of rFSH from the start of stimulation was associated with reduced variability in follicle size at time of oocyte maturation trigger and an increased number of mature oocytes retrieved.

Non-equivalence of anti-Müllerian hormone automated assays-clinical implications for use as a companion diagnostic for individualised gonadotrophin dosing

STUDY QUESTION

Can anti-Müllerian hormone (AMH) automated immunoassays (Elecsys® and Access) be used interchangeably as a companion diagnostic for individualisation of follitropin delta dosing?

SUMMARY ANSWER

The Access assay gives systematically higher AMH values than the Elecsys® assay which results in over 29% of women being misclassified to a different follitropin delta dose.

WHAT IS KNOWN ALREADY

Follitropin delta is the first gonadotrophin to be licenced with a companion diagnostic, the Roche Elecsys® AMH Plus assay. Alternative automated AMH assays including the Beckman Coulter Access immunoassay are considered to provide similar results, but clarification of their suitability as an off-licence companion diagnostic for follitropin delta is required.

STUDY DESIGN, SIZE, DURATION

We systematically searched the existing literature for studies that had measured AMH using both automated assays in the same cohort of women. Individual paired patient data were acquired from each author and combined with unpublished data.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We identified five eligible prospective published studies and one additional unpublished study. A 100% response from the authors was achieved. We collected paired AMH data on samples from 848 women. Passing-Bablok regression and Bland-Altman plots were used to compare the analytical performance of the two assays. The degree of misclassification to different treatment categories was estimated should the Access AMH be used as a companion diagnostic instead of the Elecsys AMH in determining the dosing of follitropin delta.

MAIN RESULTS AND THE ROLE OF CHANCE

The Passing-Bablok regression shows a linear relationship (Access = -0.05 + 1.10 × Elecsys). The Access assay systematically gave higher values by an average of 10% compared with the Elecsys assay (slope = 1.10, 95% CI: 1.09 to 1.12). The average of the difference between the two assays was 2.7 pmol/l. The 95% limits of agreement were -11.7 to 6.3. Overall 253 (29.3%) women would have received an inappropriate follitropin delta dose if the Beckman Coulter Access assay was used. Specifically, a substantial proportion of women (ranging from 49% to 90% depending on the AMH category) would receive a lower dose of follitropin delta based on the Access AMH assay. Up to 10% (ranging from 2.5% to 10%) of women with high ovarian reserve would have been misclassified to a greater dose of follitropin delta based on the Access AMH assay.

LIMITATIONS REASONS FOR CAUTION

We compared the values of the two principal automated assays, extrapolation of our findings to other automated AMH assays would require similar comprehensive examination.

WIDER IMPLICATIONS OF THE FINDINGS

An international standard for the calibration of the automated AMH assays is warranted to facilitate efficient use of AMH as a companion diagnostic. The variable calibration of alternative automated AMH assays may adversely impact on the performance of the follitropin delta dosing algorithm.

STUDY FUNDING/COMPETING INTEREST(S)

No formal funding has been received for this study. SI is funded by a UK Medical Research Council skills development fellowship (MR/N015177/1). SMN has received speakers fees, travel to meetings and participated in advisory Boards for Beckman Coulter, IBSA, Ferring Pharmaecuticals, Finox, Merck Serono, Merck and Roche Diagnostics. SMN has received research support from Ansh laboratories, Beckman Coulter, Ferring Pharmaceuticals and Roche Diagnostics.

TRIAL REGISTRATION NUMBER

N/A.

Luteal phase progesterone and oestradiol after ovarian stimulation: relation to response and prediction of pregnancy

Research has focused on optimizing luteal phase support and endometrial receptivity in ovarian stimulation cycles. In this study, serial endocrine measurements were taken in 600 patients after a gonadotrophin-releasing hormone antagonist stimulation protocol. On the day of blastocyst transfer, serum progesterone and oestradiol were similar irrespective of a subsequent positive or negative pregnancy test (median 99 ng/ml versus 103 ng/ml for progesterone, respectively) or a subsequent live birth or pregnancy loss. Serum progesterone was significantly correlated to each ovarian response parameter (total number of follicles, number of oocytes retrieved and oestradiol concentration; r = 0.45, 0.57 and 0.54 respectively, all P < 0.0001). These correlations were consistent irrespective of clinical outcome. On the day of the pregnancy test, these correlations had vanished except in the live birth subgroup showing a weaker correlation (r = 0.22, 0.27 and 0.32 respectively, all P < 0.005). The lowest HCG and progesterone levels associated with live birth were 59.3 IU/l and 12.3 ng/ml, respectively. Fourteen out of 92 patients (15.2%) with pregnancy loss had normal HCG but low progesterone levels (above and below their respective 5th percentile), and miscarried before the end of the 7th week, when the luteal-placental shift occurs.

Comparative pharmacology of a new recombinant FSH expressed by a human cell line

Recombinant FSH proteins are important therapeutic agents for the treatment of infertility, including follitropin alfa expressed in Chinese Hamster Ovary (CHO) cells and, more recently, follitropin delta expressed in the human cell line PER.C6. These recombinant FSH proteins have distinct glycosylation, and have distinct pharmacokinetic and pharmacodynamic profiles in women. Comparative experiments demonstrated that follitropin delta and follitropin alfa displayed the same in vitro potency at the human FSH receptor, but varied in their pharmacokinetics in mouse and rat. While follitropin delta clearance from serum depended in part on the hepatic asialoglycoprotein receptor (ASGPR), follitropin alfa clearance was unaffected by ASGPR inhibition in rat or genetic ablation in mice. The distinct properties of follitropin delta and follitropin alfa are likely to contribute to the differing pharmacokinetic and pharmacodynamic profiles observed in women and to influence their efficacy in therapeutic protocols for the treatment of infertility.

Clinical Applications of Gonadotropins in the Male

The pituitary gonadotropins, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) play a pivotal role in reproduction. The synthesis and secretion of gonadotropins are regulated by complex interactions among several endocrine, paracrine, and autocrine factors of diverse chemical structure. In men, LH regulates the synthesis of androgens by the Leydig cells, whereas FSH promotes Sertoli cell function and thereby influences spermatogenesis. Gonadotropins are complex molecules composed of two subunits, the α- and β-subunit, that are noncovalently associated. Gonadotropins are decorated with glycans that regulate several functions of the protein including folding, heterodimerization, stability, transport, conformational maturation, efficiency of heterodimer secretion, metabolic fate, interaction with their cognate receptor, and selective activation of signaling pathways. A number of congenital and acquired abnormalities lead to gonadotropin deficiency and hypogonadotropic hypogonadism, a condition amenable to treatment with exogenous gonadotropins. Several natural and recombinant preparations of gonadotropins are currently available for therapeutic purposes. The difference between natural and the currently available recombinant preparations (which are massively produced in Chinese hamster ovary cells for commercial purposes) mainly lies in the abundance of some of the carbohydrates that conform the complex glycans attached to the protein core. Whereas administration of exogenous gonadotropins in patients with isolated congenital hypogonadotropic hypogonadism is a well recognized therapeutic approach, their role in treating men with normogonadotropic idiopathic infertility is still controversial. This chapter concentrates on the main structural and functional features of the gonadotropin hormones and how basic concepts have been translated into the clinical arena to guide therapy for gonadotropin deficit in males.