Luteinizing hormone pulsatility in subjects with 5-alpha-reductase deficiency and decreased dihydrotestosterone production

Genome analyses and androgen quantification for an infant with 5α-reductase type 2 deficiency

OBJECTIVES

5α-reductase type 2 deficiency due to biallelic SRD5A2 variants is a common form of 46,XY disorders of sex development.

CASE PRESENTATION

A Chinese neonate presented with ambiguous genitalia. He carried a homozygous likely_pathogenic SRD5A2 variant (c.650C>A, p.A217E). His apparently nonconsanguineous parents were heterozygotes for the variant. The variant has previously been identified in two Chinese patients. Our patient carried 14.2 Mb loss-of-heterogeneity regions distributed in the genome. The SRD5A2 variant in this family was invariably coupled with two polymorphisms in exon 1 and intron 1. In the patient, blood testosterone (T)/5α-dihydrotestosterone (5αDHT) ratios were elevated before and during mini puberty, and were higher when measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) than measured by conventional immune assays.

CONCLUSIONS

This study provides evidence for the founder effect of an SRD5A2 variant. Furthermore, our data indicate that there is a need to establish a new reference value for T/5αDHT ratios using LC-MS/MS.

Testosterone's short-term positive effect on luteinizing-hormone secretory-burst mass and its negative effect on secretory-burst frequency are attenuated in middle-aged men

BACKGROUND

Testosterone (T) production declines and LH pulses become smaller and more frequent in middle-aged men. The mechanisms underlying these changes are not known.

RATIONALE

Small frequent LH pulses in middle-aged men could reflect impaired feedback by systemic T.

HYPOTHESIS

Middle age disrupts negative feedback by T on selected facets of LH secretion.

SUBJECTS AND SETTING

Healthy men were studied at an academic medical center.

METHODS

The protocol comprised blockade of gonadal steroidogenesis and graded transdermal addback of T doses of 0, 2.5, 5, or 7.5 mg/d designed to span the castrate to physiological range of T concentrations in each of 23 healthy men ages 19-71 yr (interquartile range, 28-53 yr). We quantified 12-h basal and pulsatile LH secretion (92 time series) using a mathematically justified deconvolution method.

RESULTS

Stepwise T supplementation from the hypogonadal through the eugonadal range repressed mean (12-h) LH concentrations (P = 0.001). By regression analysis, age attenuated the capabilities of increasing T concentrations to 1) increase LH secretory-burst mass (P < 0.0001); and 2) decrease LH secretory-burst frequency (P = 0.025). Age did not alter T's feedback on basal LH secretion, interpulse regularity, the waveform of LH secretory bursts, or the slow half-life of LH.

CONCLUSION

Middle age impairs both the positive and negative actions of systemic T on pulsatile LH secretion in healthy men, thus potentially explaining earlier inconsistencies in feedback studies based upon single-sample mean LH concentrations. Longitudinal studies will be required to elucidate the precise age dependence of inferred dual feedback failure.

Pharmacokinetics and pharmacodynamics of oral testosterone enanthate plus dutasteride for 4 weeks in normal men: implications for male hormonal contraception

Oral administration of testosterone enanthate (TE) and dutasteride increases serum testosterone and might be useful for male hormonal contraception. To ascertain the contraceptive potential of oral TE and dutasteride by determining the degree of gonadotropin suppression mediated by 4 weeks of oral TE plus dutasteride, 20 healthy young men were randomly assigned to 4 weeks of either 400 mg oral TE twice daily or 800 mg oral TE once daily in a double-blinded, controlled fashion at a single site. All men received 0.5 mg dutasteride daily. Blood for measurement of serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone, dihydrotesterone (DHT), and estradiol was obtained prior to treatment, weekly during treatment, and 1, 2, 4, 8, 12, 13, 14, 16, 20, and 24 hours after the morning dose on the last day of treatment. FSH was significantly suppressed throughout treatment with 800 mg TE once daily and after 4 weeks of treatment with 400 mg TE twice daily. LH was significantly suppressed after 2 weeks of treatment with 800 mg TE, but not with 400 mg TE. Serum DHT was suppressed and serum estradiol increased during treatment in both groups. High-density lipoprotein cholesterol was suppresed during treatment, but liver function tests, hematocrit, creatinine, mood, and sexual function were unaffected. The administration of 800 mg oral TE daily combined with dutasteride for 28 days significantly suppresses gonadotropins without untoward side effects and might have utility as part of a male hormonal contraceptive regimen.