8.2.1 Aetiopathogenesis

HH can be acquired (AHH) due to a number of different pathological conditions or congenital (CHH) due to genetic factors (Figure 8.1).

Figure 8.1 Hypogonadotropic Hypogonadism FSH treatment.

Acquired HH can be of organic or functional origin. Concerning the first group, these are destructive, infiltrative or infectious hypothalamus or pituitary lesions, micro- or macroadenomas of the pituitary gland, empty sella syndrome, encephalic trauma, and pituitary/brain radiation. Functional causes of AHH are related to exhausting exercise, or drug intake (e.g. anabolic steroids, glucocorticoids, antipsychotic agents – which interfere with the dopaminergic system – opioids, androgens) [4]. Nutritional disorders might have a negative effect on hypothalamic GnRH secretion with the consequent HH. A frequent cause of AHH is hyperprolactinemia due to the intake of antipsychotic drugs or hypothyroidism.

Congenital hypogonadotropic hypogonadism (CHH) is a rare and phenotypically heterogeneous condition with an incidence of 1:8,000 in male individuals.

The pathophysiology of CHH may derive from: (i) abnormal differentiation, development or migration of GnRH neurons during foetal development; or (ii) signalling abnormalities that involve neuroendocrine factors necessary for GnRH secretion or responsiveness to the stimulatory effects of GnRH on gonadotrope pituitary cells [5]. From a clinical point of view, CHH can be divided into: (i) Kallmann syndrome (KS), which is associated with decreased sense of smell (anosmia or hyposmia) and other non-olfactory and non-reproductive anomalies/malformations; and (ii) normosmic (nCHH). Phenotypical manifestations common to the two forms are absent or delayed puberty, sparse secondary sexual characteristics, such as absent body hair, high-pitched voice, reduced muscle mass, micropenis, very low testicular volume (<5 ml), and history of cryptorchidism. The clinical appearance depends on the onset of the disease, that is, patients with an infancy onset often have all the above-mentioned severe manifestations, whereas patients with later onset of the disease may have only reduced spermatogenesis and mild hypoandrogenism [6].

CHH is a multifactorial, polygenic disease involving over 35 genes [5,7]. The discovery of novel genes is currently ongoing, thanks to the diffusion of Next Generation Sequencing (NGS) platforms; however, in about 50% of cases the aetiology still remains unknown. A peculiarity of this genetic disease is that CHH does not always follow the classical Mendelian (autosomal dominant, autosomal recessive or X-linked) inheritance pattern. In about 15–20% of cases, a digenic or oligogenic way of transmission has been described, referring to an even more complex mode of transmission. In these cases, the combined effect of heterozygous mutations in more than one gene is responsible for the phenotype. Interestingly enough, different clinical manifestations can be caused by mutations in the same gene (e.g. FGFR1 and PROKR2), indicating that from a genetic point of view a clear-cut distinction between KS and nCHH cannot be always made [6].

8.2.2 Therapy in HH

Discovering the aetiology behind HH is relevant since treatment options may change substantially. For instance, the therapy of AHH is often based on the removal of the noxa and the treatment of the underlying disease such as surgical removal of an adenoma or medical therapy (i.e. substitutive therapy with levotiroxin in hypothyroidism or dopamine agonist in cases of hyperprolactinemia).

In all CHH patients and in those AHH patients in whom the HPG axis cannot be restored, spermatogenesis can be induced by hormone therapy (either long-term pulsatile GnRH administration or subcutaneous gonadotropin injections). With both available therapeutical options, a positive response can be obtained in the majority of affected individuals. However, because of the limitations of GnRH pumps, gonadotropins are much more commonly used in general patient care. The onset and the severity of the neuroendocrine defect is a relatively good predictor for responsiveness. Negative prognostic factors are typical features of childhood onset CHH, such as very low testis volume (TV ≤4 ml), low serum levels of inhibin B, uni- or bilateral cryptorchidism, or micropenis [4]. According to two large studies, predictors for favourable response are larger baseline testicular volume, BMI of less than 30, advanced sexual maturity, the absence of adverse fertility factors and the absence of multiple pituitary hormone deficiency [8,9].

Treatment strategies include exogenous gonadotropins: (i) hCG monotherapy (± adjuvant FSH); (ii) combined hCG + FSH therapy; and (iii) sequential gonadotropin treatment with FSH priming followed by hCG:

1. 
   

   1. hCG monotherapy: (1,000–1,500 IU/2–3 times/week) is usually advised for individuals with mild HH, thus TV>4 ml and/or no history of cryptorchidism. If the patient remains azoospermic, even after 3–6 months of treatment, FSH supplementation is needed [4,5].

   
   
2. 
   

   2. Combined gonadotropin therapy: with hCG (1,000–1,500 IU/2–3 times/week) and FSH (75–150 IU/2–3 times/week) is the “gold-standard” for patients with pre-pubertal TV (≤4 ml) [4,5].

   
   
3. 
   

   3. FSH priming followed by hCG: appears to be a promising regimen to improve sperm parameters in men with a severe form of CHH. A 2–4 months FSH-priming stimulates Sertoli and spermatogonial cell proliferation with consequent increase of TV and hCG can be added when TV reaches around 8 ml [4,5].

The first signs of an efficient therapy can be observed after 3–6 months, but fertility-induction may take up to 24 months to reach the maximal effect. Especially, CHH patients with cryptorchidism or those with a TV of less than 4 ml require extended courses of treatment, around 18–24 months [10,11]. Similarly, HH men who have been pre-treated with testosterone have a slower achievement of spermatogenesis and of conception in respect to testosterone “naïve” patients [12].

The majority of HH patients will achieve spermatogenesis under gonadotropin treatment and may generate their own biological child. Although sperm count is usually in the range of oligozoospermia, qualitative sperm parameters are normal, allowing a relatively high chance to achieve natural pregnancy. On the other hand, if the sperm parameters are poor, Assisted Reproductive Technology (ART) treatments, such as in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), can be performed. In cases of azoospermia, testicular sperm extraction (TESE or micro-TESE) may be offered to the patients with subsequent ICSI.

CHH cases imply the need for genetic testing and genetic counselling in order to inform the couple about the risks of transmission of mutation(s) and about the health consequences on the offspring. However, due to the complexity of the genetic architecture of this disease the prediction of the offspring’s phenotype remains difficult. In the case where the mutation is identified, and it follows the Mendelian inheritance mode, preimplantation genetic testing should be advised for the couple. If this is not feasible, during counselling they should be informed about the importance of the screening for “minipuberty” in their offspring. The lack of “minipuberty” will allow an early diagnosis and consequently a timely intervention for pubertal induction in adolescence with consequent improvement of sexual and reproductive function in adulthood.

8.3.1 Introduction

Idiopathic infertility represents the most commonly observed form of infertility in clinical practice, but unfortunately, rational treatments are lacking. Idiopathic male infertility commonly is represented by oligo-astheno-teratozoospermia (OAT) and the goal of treatment should therefore be the restoration of a quantitative and qualitative normal spermatogenesis. Although ICSI is often regarded as a treatment for infertile men with severe OAT, treatments able to restore the natural fertility would be the primary choice. As FSH acts mainly on the first step of spermatogenesis and represents a successful, rational treatment in HH, it is frequently also offered to men with male normogonadotropic infertility based on the hypothesis that spermatogenesis could be stimulated by increasing gonadotropin levels.

Nevertheless, too often male infertility is not adequately assessed and diagnosed, and there is a general conviction among non-experts that this condition could not be treatable and it is preferable to routinely apply ART. On the other hand, novel strategies for treating male infertility are needed, so that therapies could be converted from empiric into rational therapy. The currently most promising approach to treat male infertility is to stimulate spermatogenesis by FSH treatment. However, it is also clear from many studies published so far that FSH treatment is not indicated for all infertile men, and also in selected patients the effects are not easily predictable. One of the most challenging aspects in this field is, therefore, the identification of the “perfect” patient, that is the patient with the highest probability to respond to treatment. A personalized treatment regimen, which takes into account clinical and genetic factors controlling spermatogenesis, might resemble the most promising approach to this aim [13].

Numerous studies have been published in the last decades, from observational studies, to more recent randomized, multicentre, controlled studies and pharmacogenetic studies [13]. As outlined below, studies differ in patient selection criteria, duration and dosage of therapy, primary and secondary outcome, and have been conducted either with purified FSH (pFSH), highly purified FSH (hpFSH), or recombinant FSH (rhFSH). Therefore, comparison between published data is not immediate, although recent meta-analyses have been performed and guidelines from scientific societies have been produced [3,14].

8.3.2 General Effect of FSH Treatment

In general, the effectiveness of FSH therapy in male-factor infertility has been reported by some authors in terms of significant improvements in sperm quantity/quality and/or pregnancy rates (reviewed in [3,13–16], whereas other authors reported no effect. A meta-analysis by the Cochrane Collaboration [17], only including randomized controlled trials (RCTs), showed that infertile men who received FSH had a significant increase in spontaneous pregnancy rate per couple with respect to patients receiving placebo or no treatment. In another meta-analysis [16], including all available controlled clinical trials, FSH was shown to significantly increase sperm concentration and quality, and spontaneous and ART-related pregnancy rate. A more recent review and meta-analysis [15] on the benefits of medical therapy in couples with idiopathic male subfertility concludes that FSH is among the few empirical therapies with a demonstrated role in improving semen parameters.

Guidelines from the European Academy of Andrology for the management of OAT [14] suggest that treatment with FSH can be offered to selected men from infertile couples (normogonadotropic men with idiopathic oligozoospermia or OAT) in an attempt to improve quantitative and qualitative sperm parameters and pregnancy rate, with low evidence. In a position statement for the Italian Society of Andrology and Sexual Medicine, Barbonetti [3] also suggests the use of FSH to increase sperm concentration and motility in infertile normogonadotropic men with idiopathic oligozoospermia or OAT, with moderate evidence grading.

8.3.3 Selection of Candidate Patients and Predictors of Response

In general, the most important aspect to consider in the clinical practice is not proscribing FSH to all infertile men at random without an adequate diagnostic work-up. It is clear from all published studies that FSH is not effective in all infertile men, neither in all OAT patients. To increase the chance of response to treatment, patient selection is essential (Figure 8.2).

Figure 8.2 Idiopathic infertility FSH treatment.

First, FSH treatment is not recommended in azoospermic men (apart from HH cases, as described above) and in men with obstructive/sub-obstructive forms of infertility. Although the rationale not to treat these men is obvious, it implies that diagnostic procedures in infertile men should be applied to clearly distinguish patients with these characteristics from men with secretory (testicular) forms of OAT. Therefore, history, physical examination, reproductive hormone levels, imaging studies, and, when appropriate, genetic studies should be carried out before considering a patient candidate for FSH treatment. One of the most important parameters to identify patients who will certainly not respond to FSH treatment, is the plasma concentration of FSH, taking into consideration that the high levels of this hormone are a strong indicator that primary testicular damage exists, and a further increase of FSH with an exogenous drug is not able to overcome the spermatogenic impairment. Therefore, FSH treatment is suggested only in infertile men with idiopathic oligozoospermia or OAT and normal FSH plasma levels (normogonadotropic) [3,18]. Traditionally, normal FSH levels are considered when up to 8 IU/L.

Obviously, FSH treatment should be considered only when the couple have no female infertility causes. This does not mean that FSH cannot be considered when assisted reproduction techniques are already necessary for the couple, but a comprehensive female evaluation should be performed and the decision on whether to proceed with FSH treatment should be made collegially with the couple, the gynaecologist and andrologist.

Other than sperm count and motility, FSH has been suggested to improve pregnancy (natural and by assisted techniques) by ameliorating sperm chromatin integrity and fertilizing ability [19–22]. Therefore, idiopathic infertile patients exhibiting high values of sperm DNA fragmentation might represent a class of responder men. However, only one RCT had a DNA fragmentation index as the primary endpoint [23], and suggested that the improvement in this parameter is dependent on the p.N680S allele of the FSH receptor (FSHR) gene (see Section 8.3.4). While results on sperm DNA fragmentation are therefore encouraging, FSH therapy does not seem to be clearly associated with a reduction of chromosomal aneuploidies [21,24]. Therefore, this parameter, generally assessed by FISH, seems not to be of predictive value.

Other parameters that might be useful in the selection of patients and identification of responders and non-responders might be related to the specific alteration of spermatogenesis underlying oligozoospermia. In fact, low sperm count might be actually due to hypospermatogenesis (reduced number of germ cells) and/or alteration in the maturation process of germ cells (spermatogenic arrest). Two studies, performed by the same research group, demonstrated that the knowledge of the spermatogenic alteration by testicular fine needle aspiration cytology allows predicting the response to FSH therapy in oligozoospermic patients [25,26]. In fact, these studies showed that a pre-treatment testicular cytology characterized by hypospermatogenesis (without associated maturation disturbances) was associated with better response to FSH treatment with respect to hypospermatogenesis associated with partial maturation arrest at the spermatid level. These findings could be interpreted in the light of the demonstration that FSH therapy increased mainly the spermatogonial population [25], therefore being effective in stimulating final sperm production, particularly when the entire process of spermatogenesis is only quantitatively altered.

To overcome the intrinsic difficulties in examining the testicular structure, the same group proposed the analysis of spermatid count in the semen as a marker of maturation disturbance of spermiogenesis [27]. The authors showed that FSH therapy allowed significant improvement in sperm parameters and natural or assisted fertility in patients with lower spermatid count, therefore suggesting the evaluation of this parameter to predict the response to FSH therapy. Validation studies are awaited in order to introduce this parameter into clinical practice.