Evaluation of pituitary gonadotropic function in men: value of luteinizing hormone-releasing hormone response versus basal luteinizing hormone level for discrimination of diagnosis

Dynamic GnRH and hCG testing: establishment of new diagnostic reference levels

OBJECTIVE

Gonadotropin-releasing hormone (GnRH) and human chorionic gonadotropin (hCG) stimulation tests may be used to evaluate the pituitary and testicular capacity. Our aim was to evaluate changes in follicular-stimulating hormone (FSH), luteinizing hormone (LH) and testosterone after GnRH and hCG stimulation in healthy men and assess the impact of six single nucleotide polymorphisms on the responses.

DESIGN

GnRH and hCG stimulation tests were performed on 77 healthy men, 18-40 years (reference group) at a specialized andrology referral center at a university hospital. The potential influence of the tests was illustrated by results from 45 patients suspected of disordered hypothalamic-pituitary-gonadal axis.

METHODS

Baseline, stimulated, relative and absolute changes in serum FSH and LH were determined by ultrasensitive TRIFMA, and testosterone was determined by LC-MS/MS.

RESULTS

For the reference group, LH and FSH increased almost 400% and 40% during GnRH testing, stimulated levels varied from 4.4 to 58.8 U/L and 0.2 to 11.8 U/L and FSH decreased in nine men. Testosterone increased approximately 110% (range: 18.7-67.6 nmol/L) during hCG testing. None of the polymorphisms had any major impact on the test results. Results from GnRH and hCG tests in patients compared with the reference group showed that the stimulated level and absolute increase in LH showed superior identification of patients compared with the relative increase, and the absolute change in testosterone was superior in identifying men with Leydig cell insufficiency, compared with the relative increase.

CONCLUSIONS

We provide novel reference ranges for GnRH and hCG test in healthy men, which allows future diagnostic evaluation of hypothalamic-pituitary-gonadal disorders in men.

Value of gonadotropin-releasing hormone testing in the differential diagnosis of androgen deficiency in elderly men

Elderly men with low testosterone (T) levels are increasingly diagnosed to have partial androgen deficiency of the aging male (PADAM). Frequently, magnetic resonance imaging is performed to exclude pituitary adenoma. The value of GnRH testing to differentiate PADAM from secondary hypogonadism is unknown. Serum levels of T as well as LH and FSH at baseline and after GnRH were evaluated in the following groups: 1) 24 elderly men with low serum T (<11.7 nmol/liter), 2) 25 elderly men with normal serum T levels (>11.7 nmol/liter), 3) 10 men with primary hypogonadism, 4) 24 men with secondary hypogonadism, and 5) 13 healthy young volunteers. In elderly men, T levels were lower (P < 0.001) and gonadotropin levels higher (P = 0.03) compared with younger controls. LH and FSH response to GnRH was higher in elderly men with low T levels (PADAM) compared with elderly men with normal T levels (P = 0.02 and P < 0.001) in the presence of similar basal gonadotropin levels. To differentiate secondary hypogonadism from PADAM with a sensitivity of 100%, a T less than 10 nmol/liter had a specificity of 50%. This specificity was improved to 75% by using a cutoff of less than or equal to 15 mU/liter increase of LH upon GnRH stimulation. Overall, decreased T levels and increased LH levels in elderly men suggest a primary Leydig cell dysfunction. In the subgroup of elderly men with low T levels, an increased LH response to GnRH with normal basal LH levels suggests additional, possibly hypothalamic changes. To exclude secondary hypogonadism in PADAM, diagnostic accuracy can be improved by using GnRH testing.

Impaired spermatogenesis: an unrecognized feature of cartilage-hair hypoplasia

BACKGROUND

Cartilage-hair hypoplasia (CHH), an autosomal recessive chondrodysplasia, is characterized by severe growth failure, hypoplastic hair, impaired immunity, and deficient erythropoiesis. These features may result from a generalized defect in cell proliferation.

AIM

In order to investigate whether an impairment of cell proliferation is present in spermatogenesis, we analysed fertility in a clinical and laboratory study of adult males with CHH.

METHODS

Eleven adult males (median age 29 years, range 21-49 years) with CHH were included in the study. The patients were examined clinically for testicular volume and other clinical characteristics. Blood samples were collected to determine serum concentrations of sex hormones, sex hormone-binding globulin, inhibin B and gonadotrophins (basal and gonadotrophin-releasing hormone-stimulated). Semen samples were analysed for volume, sperm concentration, motility, morphology, and antibody status.

RESULTS

The testicular size was subnormal in some patients, but the serum concentrations of testosterone, inhibin B and gonadotrophins were usually normal. The semen analyses were not within normal limits in any of the patients, as indicated by low sperm concentration, decreased motility and/or morphological changes.

CONCLUSIONS

The defect in cell proliferation in men with CHH also involves the spermatogenic cells and is evident as an impairment of spermatogenesis.

The hypothalamus-pituitary-gonad axis and testicular function in male patients after treatment for haematological malignancies

OBJECTIVE

The effect of aggressive chemotherapy on the hypothalamus-pituitary-gonad axis and on testicular function was assessed in nine male patients who had received chemotherapy only (CT, group I) and in 10 males after allogeneic bone marrow transplantation (BMT, group II). The mean time from CT or BMT to the assessment was 3.7 (range, 1.0-11.7) years.

DESIGN

The responses of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were assessed by the gonadotropin-releasing hormone (GnRH) test and, in addition, serum basal values for testosterone and sex hormone binding globulin (SHBG) were measured and the free androgen index (FAI) was calculated. In 13/19 patients the human chorionic gonadotropin (hCG) test was performed.

RESULTS

In group I, only one patient had an abnormal basal FSH value, but all (100%) had pathologically poor responses to the GnRH test. In contrast, all baseline FSH values were raised in group II (mean, 18; range, 11-30 U L-1), indicating toxic injury to the seminiferous tubules. Also in group II the responses to GnRH weer low throughout the test (90%) and there were no clear peak values. In group II, the basal FSH and its maximum response to GnRH were significantly more affected than in group I (P < 0.001). The difference may be due to the effect of the conditioning regimen. Serum basal LH was raised in three of the patients in group I and they also had abnormal releasing test responses. In group II, baseline LH was abnormal in four patients, but the responses to GnRH were normal. However, the maximum responses to the releasing test was significantly more affected in group II (P = 0.024). Serum testosterone levels were normal in all test subjects in both study groups. However, in two patients in both groups, the serum free androgen index was below the low reference limit, and an impaired response of serum testosterone to hCG stimulation was common (60%).

CONCLUSIONS

A toxic injury in the testis is common in haematological patients, especially after high-dose chemoradiotherapy. Serum basal testosterone usually remains normal, but even then subnormal serum free androgen index, impaired testosterone response to hCG injection and abnormal response in LH may indicate a deficient androgen status. It may well be that testosterone replacement therapy should be considered in these cases.

The effect of androgen blockade on pulsatile gonadotrophin release and LH response to naloxone

In order to clarify the effects of androgen blockade on the hypothalamic-pituitary-testicular axis in man, four patients with advanced prostate cancer, not previously treated, were given oral flutamide, 250 mg three times daily for 9 days. Before, and 7, 8 and 9 days after starting flutamide treatment, on separate days, the following tests were performed: a gonadotrophin pulsatility study, with 20 min interval blood sampling for 12 h, a naloxone test and a GnRH test. Flutamide induced a significant increase in both LH and FSH pulse frequency, while pulse amplitudes and plasma integrated concentrations (IC) of LH and FSH were unaffected. Plasma integrated concentrations of testosterone and oestradiol rose significantly, while that of prolactin was unaffected. The increase in plasma LH concentration induced by naloxone injection was abolished by flutamide treatment. On the other hand, the small FSH response to naloxone was unaffected by flutamide treatment. Response to GnRH was unaffected by flutamide. These results suggest that flutamide exerts effective androgen blockade at the hypothalamic level, since, despite increased plasma testosterone concentrations, gonadotrophin pulse frequency increased and the LH response to naloxone was abolished.

Luteinizing hormone and follicle-stimulating hormone responses to intransal gonadotropin-releasing hormone

For determination of the dose-response relationships of plasma luteinizing hormone (LH) and follicle-stimulating hormone (FSH) to the intranasal administration of gonadotropin-releasing hormone (GnRH), normal adult men were administered doses of 100, 200, 400, and 800 micrograms of GnRH on separate days, and plasma LH and FSH were measured before and after nasal insufflation of GnRH. Plasma LH was increased after a minimum dose of 200 micrograms GnRH. Median peak plasma LH levels occurred 30 minutes after intranasal GnRH and followed a log-dose relationship. When compared with intravenous GnRH, the biopotency of intranasal GnRH at the 200-, 400-, and 800-microgram doses was 1.1%, 2.3%, and 6.2%, respectively. Plasma FSH levels rose significantly only after the highest (800-micrograms) intranasal GnRH dose. From these data, we conclude that in eugonadal adult men the minimal effective dose of intranasal GnRH to elicit a significant pituitary (LH) response is 200 micrograms and that the relative efficacy of intranasal GnRH increases with the dose. In spite of the apparently low biopotency for intranasal GnRH, this route of administration may be considered as an alternative to the parenteral mode of GnRH delivery, and the lower biopotency can be partly overcome by increasing the dose.

Is there hypothalamic-pituitary-gonadal dysfunction in paedophilia? A pilot study

The hypothalamic - pituitary - gonadal axis was evaluated in men with paedophilia and non-paedophilic paraphilia, and in normal male controls, by infusion of 100 mcg. of synthetic luteinising hormone-releasing hormone (LHRH). There were no significant differences among groups in age, height, weight, testosterone, baseline luteinising hormone (LH) and follicle stimulating hormone (FSH), and FSH response to LHRH. However, there was a significant difference between the paedophilic group and the other two groups in the LH response to LHRH. The paedophiles responded with a marked elevation of LH, when compared with the non-paedophilic paraphiliacs and controls. These data indicate a hypothalamic - pituitary - gonadal dysfunction in paedophiles.