The role of growth hormone in male infertility

Effects of Growth Hormone on Adult Human Gonads: Action on Reproduction and Sexual Function

Growth hormone (GH), which is commonly considered to be a promoter of growth and development, has direct and indirect effects on adult gonads that influence reproduction and sexual function of humans and nonhumans. GH receptors are expressed in adult gonads in some species including humans. For males, GH can improve the sensitivity of gonadotropins, contribute to testicular steroidogenesis, influence spermatogenesis possibly, and regulate erectile function. For females, GH can modulate ovarian steroidogenesis and ovarian angiogenesis, promote the development of ovarian cells, enhance the metabolism and proliferation of endometrial cells, and ameliorate female sexual function. Insulin-like growth factor-1 (IGF-1) is the main mediator of GH. In vivo, a number of the physiological effects of GH are mediated by GH-induced hepatic IGF-1 and local IGF-1. In this review, we highlight the roles of GH and IGF-1 in adult human gonads, clarify potential mechanisms, and explore the efficacy and the risk of GH supplementation in associated deficiency and assisted reproductive technologies. Besides, the effects of excess GH on adult human gonads are discussed as well.

Growth Hormone and Insulin-Like Growth Factor Action in Reproductive Tissues

The role of growth hormone (GH) in human fertility is widely debated with some studies demonstrating improvements in oocyte yield, enhanced embryo quality, and in some cases increased live births with concomitant decreases in miscarriage rates. However, the basic biological mechanisms leading to these clinical differences are not well-understood. GH and the closely-related insulin-like growth factor (IGF) promote body growth and development via action on key metabolic organs including the liver, skeletal muscle, and bone. In addition, their expression and that of their complementary receptors have also been detected in various reproductive tissues including the oocyte, granulosa, and testicular cells. Therefore, the GH/IGF axis may directly regulate female and male gamete development, their quality, and ultimately competence for implantation. The ability of GH and IGF to modulate key signal transduction pathways such as the MAP kinase/ERK, Jak/STAT, and the PI3K/Akt pathway along with the subsequent effects on cell division and steroidogenesis indicates that these growth factors are centrally located to alter cell fate during proliferation and survival. In this review, we will explore the function of GH and IGF in regulating normal ovarian and testicular physiology, while also investigating the effects on cell signal transduction pathways with subsequent changes in cell proliferation and steroidogenesis. The aim is to clarify the role of GH in human fertility from a molecular and biochemical point of view.

Cetrorelix suppression test in the diagnostic work-up of severe hyperandrogenism in adolescence

Conventional diagnostic procedures failed to provide a definitive diagnosis in a 15 year-old girl presenting with severe hirsutism, oligomenorrhea, and markedly elevated serum testosterone levels. To examine whether androgen overproduction was luteinizing hormone (LH) dependent and thus likely of ovarian origin we performed a new test to suppress LH secretion based on the use of Cetrorelix, a short-acting gonadotropin-releasing hormone antagonist. Subcutaneous administration of Cetrorelix 250 microg once daily for 5 days resulted in partial suppression of serum LH and testosterone. The same dose administered twice daily for 5 days almost completely suppressed serum LH and testosterone, thereby supporting a diagnosis of ovarian androgen excess. This observation was confirmed by a positive human chorionic gonadotropin stimulation test and an MRI showing bilateral polycystic ovaries.

CONCLUSION

The Cetrorelix suppression test appears to be a promising instrument to help solve the differential diagnosis of severe hyperandrogenism in adolescence.

Hormonal control of inhibin B in men

Serum inhibin B (IB) and testosterone (T) levels, secreted by Sertoli cells (SC) and Leydig cells (LC), respectively, are parameters of the functional state of these cells. Whereas LC activity and, consequently, T secretion are regulated by serum LH, factors regulating IB secretion by SC are still partially unknown. There is evidence that under certain conditions such as puberty, aging or some spermatogenesis defects, LH levels or Gn-independent factors might contribute to regulating SC activity and IB secretion. Among these factors, GH and IGF-I as well as PRL might have a role. Therefore, in order to explore the possible effects of either LH alone and FSH alone or a combination of both Gn, respectively, on SC function, IB plasma levels and spermatogenesis, we studied their effects in 6 patients with hypogonadotropic hypogonadism (HH), whereas the effects of GH on these parameters were studied in 6 men with panhypopituitarism (PH). Finally, the possible effects of PRL on SC function and spermatogenesis were studied in 6 patients with hyperprolactinemia (HPRL); 24 normal, fertile adults served as control group. In men with HH, neither human chorionic Gn (hCG) nor FSH, respectively, were able to increase serum IB after 3 months of therapy, whereas combined Gn therapy for 24 months increased IB plasma levels and stimulated spermatogenesis in 4 out of 6 hypogonadal men. In panhypopituitaric men, GH added to the classical Gn therapy did not have an additional effect on serum IB levels or spermatogenesis. Surprisingly, in our hyperprolactemic men, IB plasma levels were increased and positively correlated (p<0.01) with serum PRL levels, whereas normalization of the latter by cabergoline treatment caused a decrease of IB levels and a moderate increase in T, LH and FSH. In conclusion, the lack of SC response to FSH therapy alone, as opposed to the response to combined Gn therapy, might indicate that normalization of serum T by hCG is required to obtain IB secretion by SC. Addition of GH did not affect SC function, serum IB levels or spermatogenesis. Finally, our data suggest that PRL plasma levels might have a direct role on IB secretion, suggesting that the hypogonadism found in patients with HPRL might be a consequence of both central (inhibition of Gn secretion) and peripheral (stimulation of IB secretion) origin.

Low birth size and final height predict high sympathetic nerve activity in adulthood

OBJECTIVE

Being born small for gestational age (SGA) is associated with insulin resistance, hypertension and increased cardiovascular morbidity/mortality in adulthood. Sympathetic nerve hyperactivity is a well-known risk factor for cardiovascular disease mortality and is proposed to link insulin resistance with hypertension. The objective of this study was to test the hypothesis that sympathetic nerve activity is altered in individuals born SGA.

DESIGN

A cross-sectional, comparative study of 20 healthy adults (21-25 years old) born SGA (birth weight < -2SD score for healthy newborns) with normal and short stature, and 12 age, gender and body mass index matched individuals, born appropriate for gestational age (AGA) with normal stature.

METHODS

Direct recordings of resting sympathetic nerve activity to the muscle vascular bed (MSA) were obtained from the peroneal nerve posterior to the fibular head. Heart rate, respiration and blood pressure were recorded during the microneurographic session.

RESULTS

MSA was increased in both groups of young adults born SGA as compared to those born AGA (P < 0.05 and P < 0.005, respectively). In the combined study group MSA was inversely correlated to birth weight, length (r = -0.59, P < 0.001 and r = -0.69, P < 0.0005, respectively) and final adult height (r = -0.58; P < 0.001).

CONCLUSIONS

Being born SGA and achieving a short final height is associated with increased sympathetic nerve traffic. We suggest that the increase in sympathetic nerve traffic in young adults born SGA with normal and short stature may be the link between low birth size, hypertension and cardiovascular morbidity later in life.

Growth hormone: roles in male reproduction

Growth hormone (GH), as its name suggests, is obligatory for growth and development. It is, however, also required for sexual differentiation and pubertal maturation and participates in gonadal steroidogenesis and gametogenesis. These roles are likely to reflect the endocrine actions of pituitary GH, directly at gonadal sites and indirectly via hepatic insulin-like growth factor-1. However, because GH is also produced in gonadal tissues, it may act in paracrine or autocrine ways to regulate local processes that are strategically regulated by pituitary GH. The concept that GH is a major regulator of male reproduction is the focus of this review.

Absence of effect of recombinant growth hormone to classic gonadotropin treatment on spermatogenesis of patients with severe hypogonadotropic hypogonadism

Encouraging clinical results have suggested a complimentary or permissive role of growth hormone (GH) to gonadotropin in inducing spermatogenesis in patients with hypogonadotropic hypogonadism, who did not respond to gonadotropin therapy alone. This study evaluates the effects of GH on spermatogenesis in four azoospermic hypogonadic hypogonadotropic (HH) men, treated initially for 6 months with gonadotropins (GN) alone (phase I), followed by a 6 months cotreatment of GH with GN (phase II). Plasma testosterone (T), IGF-1 levels, testicular volume, and spermiogram were evaluated under basal conditions and every 3 months during treatment. GN treatment alone induced a significant increase of T levels and semen volume, whereas testicular volume increased very little; all patients remained azoospermic. The combined GN-GH treatment induced, as expected, an increase in IGF-1 levels and an increase of T levels to values in the normal male range as well as a further, moderate, increase in testicular volume; azoospermia persisted, however, in all patients. The data do not confirm the beneficial effects of combined GN-GH treatment in hypogonadotropic hypogonadal males reported in the literature.

Advances in the evaluation and treatment of the infertile man

Numerous advances in technology have been made in the last several years in the diagnosis and treatment of the infertile man. Using case presentations, this article highlights these important new developments and reviews the basics of a comprehensive male infertility evaluation. The use of ultrasound as a critical, indispensable, yet noninvasive tool in the evaluation of possible male reproductive tract obstruction is discussed. Since assisted reproductive techniques (ARTs) have become increasingly important in the management of the otherwise untreatable infertile man, specialized testing of sperm function, e.g., the sperm penetration assay (SPA), and strict morphology assessment are often useful prior to the initiation of some of these assisted reproductive procedures such as intrauterine insemination (IUI) or in vitro fertilization (IVF). Testicular touch preparation cytology and image analysis are also important additions to routine testicular biopsy for quantifying the extent of spermatogenesis. Finally, the revolutionary micromanipulation procedure of intracytoplasmic sperm injection (ICSI) has forever changed the practice of andrology by enabling men previously thought to be irreversibly infertile the chance to initiate their own biologic pregnancy.

Growth hormone treatment of subfertile males

OBJECTIVE

To study spermatogenesis and sperm motility during GH therapy in infertile men.

DESIGN

Prospective open study. Each patient was treated with GH for 12 weeks and followed for a total of 36 weeks with sampling of blood and semen.

SETTING

Outpatients studied at a clinical research unit of a university hospital.

PATIENTS

Nine oligozoospermic (<5 x 10(6) sperm/mL) males and nine asthenozoospermic (percentage motile sperm <30 and >15 x 10(6) sperm/mL) males. The patient groups had a significantly lower GH response to an arginine GH stimulation test as compared with a control group.

RESULTS

Serum insulin-like growth factor I (IGF-I) and serum IGF-binding protein 3 (IGFBP-3) levels increased significantly during GH treatment, as did seminal IGF-I. Serum E2, T, PRL, FSH, LH, and GH-binding protein were unchanged during the study. Sperm motility was increased significantly during GH treatment in both patient groups. There was no difference in sperm count during the treatment. There were three pregnancies in the nine couples from the asthenozoospermic group and no pregnancies in the oligozoospermic group.

CONCLUSION

The biologic and clinical results in this study encourage the initiation of double-blind, placebo-controlled trials.

Effect of growth hormone cotreatment with human chorionic gonadotropin in testicular steroidogenesis and seminal insulin-like growth factor-1 in oligozoospermia

OBJECTIVE

To study the GH synergy with hCG in testicular steroidogenesis and seminal insulin-like growth factor-1 (IGF-1) in oligozoospermia.

SETTING

University endocrine unit.

PATIENTS

Eight oligospermic, non-GH-deficient men.

INTERVENTIONS

Three different protocols spaced 3 months apart were applied in each man: plain hCG protocol: 1,500 IU IM three times every other day; GH + hCG protocol: with the addition of 4 IU SC GH daily 8 days before and throughout the hCG phase; placebo + hCG: substitution of GH by NaCL 0.9%. Blood sampling was performed before and on the 8th day (for 2nd- and 3rd-day protocols) and 24 hours after each hCG administration. Semen was collected three times during each protocol.

MAIN OUTCOME MEASURES

Plasma for P, 17-OHP, androstenedione, DHEA, DHEAS, T, and E2 and plasma and seminal IGF-1 three times during each study.

RESULTS

Serum IGF-1 levels increased more than threefold after GH administration. Seminal IGF-1 activity was unaffected by GH treatment or hCG administration, showing random fluctuations within each subject without correlation to the respective plasma levels. The incremental response of each steroid under hCG did not differ between the three protocols, apart from increased P levels under GH.

CONCLUSIONS

Short-term GH cotreatment with hCG did not affect seminal IGF-1 concentration and had a weak synergist effect on steroidogenesis.

Gonadal function and response to growth hormone (GH) in boys with isolated GH deficiency and to GH and gonadotropins in boys with multiple pituitary hormone deficiencies

OBJECTIVE

[corrected] To evaluate spermatogenesis in patients with isolated GH deficiency and multiple pituitary hormone deficiencies.

DESIGN

Treatment of isolated GH-deficient patients with recombinant human GH (weekly dose of 0.7 IU/kg) for 5.3 +/- 0.4 (mean +/- SD) years and cotreatment of multiple pituitary deficient patients with GH at the same dosage for 8.0 +/- 0.4 years and hCG (2,000 IU, three times per week) and hMG (500 IU, two times per week) for 13.7 +/- 1.1 months.

SETTING

Endocrine Pediatric Unit.

PATIENTS

Eight patients affected by isolated GH deficiency and seven by multiple pituitary hormone deficiencies.

MAIN OUTCOME MEASURES

Serum LH, FSH, and T, testicular volume, semen volume, density, count, and motility.

RESULTS

Patients with isolated GH deficiency completed their pubertal development in 19.0 +/- 3.5 months and patients with multiple pituitary hormone deficiencies in 13.7 +/- 1.1 months. At the end of puberty, the two groups of patients had similar testicular volume, penis size, sperm concentration, motility, and morphology, although T levels and seminal volume were lower in isolated GH-deficient patients than in multiple pituitary deficient patients.

CONCLUSIONS

The two groups of patients, treated specifically for their identified hormonal deficiencies, in the end had similar satisfactory reproductive results.

Statistical analysis of functional region(s) of the TSH receptor

In this study, we apply recently developed methods to evaluate the thyrotropin receptor (TSH-R). These methods are called deviation (DEV) model, deviation decrease (DD) and DEV/DD analyses, and are based on deviation of amino acid sequences. A 3-dimensional structure model of TSH-R was graphically constructed, and found to possess a large central cavity (donut-like structure). The N-terminus was found to be in the center of the whole extracellular structure and to form a part of the bottom of the cavity. High DEV values indicate deviated amino acid compositions in the protein and were seen in 7 regions, 6 of which were found to be in regions with hydrophilic and acrophilic character. On the basis of the analysis of intra-molecular cis-acting relationships, 7 pairs of regions were presumed to be closely related. Further, when 3 exoplasmic loop lesions were analyzed similarly, 3 other regions were shown to have a close relationship with the cell surface. DEV/DD values were applied to predict the interface of TSH-R with trans-acting molecules such as TSH-R antibody or TSH. The regions in association with trans-acting molecules were seen in 14 regions, 11 of which included the high DEV regions. Both of the TSH-R specific regions in the N- and C-terminal side, especially the latter, were found to be the major components.

Insulin-like growth factor I (IGF-I) and IGF binding proteins in seminal plasma before and after vasectomy in normal men

OBJECTIVE

To examine the levels and origins of insulin-like growth factor I (IGF-I) and insulin-like growth factor binding proteins (IGFBPs) in the human male genital tract.

DESIGN

Examining seminal plasma before and 3 months after vasectomy.

SUBJECTS

Fifteen men who were candidates for vasectomy were included in the study.

MAIN OUTCOME MEASURES

Seminal plasma and serum levels of IGF-I, IGFBP-1, and IGFBP-3 were determined by commercially available assays, furthermore, samples were subjected to Western ligand blotting.

RESULTS

Seminal plasma concentrations of IGF-I were significantly lower after vasectomy: 18.0 +/- 2.4 micrograms/L (before) and 12.5 +/- 1.2 micrograms/L (after). When the total ejaculate content of IGF-I was calculated, the figures were reduced by 50% after vasectomy: 45.64 +/- 7.8 ng (before) and 23.45 +/- 3.8 ng (after). The patterns observed for seminal plasma IGFBP-3 concentrations were 844.9 +/- 59 micrograms/L (before) and 816.5 +/- 65 micrograms/L (after). When the total ejaculate IGFBP-3 content was calculated there was a 36% reduction after vasectomy: 2,300 +/- 251 ng (before) and 1,474 +/- 217 ng (after).

CONCLUSIONS

A considerable amount of seminal plasma IGF-I and IGFBP-3 may be of testicular origin. Although the physiological significance of IGF-I and IGFBPs in the male reproductive system still remains uncertain, the demonstration of their presence in the testes add support to a functional role in the regulation of gonadal function.