Myotonic dystrophy type 1 presenting as male infertility

Primary amenorrhea in myotonic dystrophy type 1: Initial presentation versus incidental finding on whole genome sequencing

Myotonic dystrophy type 1 is an autosomal dominant condition due to a CTG repeat expansion in the myotonic dystrophy protein kinase (DMPK) gene. This multisystem disorder affects multiple organ systems. Hypogonadism in males affected by myotonic dystrophy is commonly reported; however, the effect on female hypogonadism remains controversial. A 19-year-old female was referred to our genetics clinic due to primary amenorrhea without any family history of similar symptoms. Initial genetics evaluation identified a variant of uncertain significance in IGSF10, c.2210T>C (p.Phe737Ser). Follow-up genetic evaluation via whole genome sequencing identified at least 100 CTG repeats in the DMPK gene, thus resulting in the diagnosis of myotonic dystrophy type 1. The patient remains otherwise asymptomatic from myotonic dystrophy. This is the first report that demonstrates primary amenorrhea as a possible presenting feature of myotonic dystrophy type 1, thus providing evidence supporting female hypogonadism in myotonic dystrophy type 1.

Hypogonadism in Males With Genetic Neurodevelopmental Syndromes

Genetic syndromes that affect the nervous system may also disrupt testicular function, and the mechanisms for these effects may be interrelated. Most often neurological signs and symptoms predominate and hypogonadism remains undetected and untreated, while in other cases, a thorough evaluation of a hypogonadal male reveals previously unrecognized ataxia, movement disorder, muscle weakness, tremor, or seizures, leading to a syndromic diagnosis. Androgen deficiency in patients with neurological diseases may aggravate muscle weakness and fatigue and predispose patients to osteoporosis and obesity. The purpose of this mini review is to provide a current understanding of the clinical, biochemical, histologic, and genetic features of syndromes in which male hypogonadism and neurological dysfunction may coexist and may be encountered by the clinical endocrinologist.

Endocrine Dysfunction in Patients With Myotonic Dystrophy

Myotonic dystrophy is a dominantly inherited multisystem disorder that results from increased CTG repeats in the 3' region of the myotonic dystrophy protein kinase gene (DMPK). The mutant DMPK mRNA remains in the nucleus and sequesters RNA-binding proteins, including regulators of mRNA splicing. Myotonic dystrophy is characterized by a highly variable phenotype that includes muscle weakness and myotonia, and the disorder may affect the function of many endocrine glands. DMPK mRNA is expressed in muscle, testis, liver, pituitary, thyroid, and bone; the mutated form leads to disruption of meiosis and an increase in fetal insulin receptor-A relative to adult insulin receptor-B, resulting in adult primary testicular failure and insulin resistance predisposing to diabetes, respectively. Patients with myotonic dystrophy are also at increased risk for hyperlipidemia, nonalcoholic fatty liver disease, erectile dysfunction, benign and malignant thyroid nodules, bone fractures, miscarriage, preterm delivery, and failed labor during delivery. Circulating parathyroid hormone and adrenocorticotropic hormone levels may be elevated, but the mechanisms for these associations are unclear. This review summarizes what is known about endocrine dysfunction in individuals with myotonic dystrophy.

Canary in the Coal Mine? Male Infertility as a Marker of Overall Health

Male factor infertility is a common problem. Evidence is emerging regarding the spectrum of systemic disease and illness harbored by infertile men who otherwise appear healthy. In this review, we present evidence that infertile men have poor overall health and increased morbidity and mortality, increased rates of both genitourinary and non-genitourinary malignancy, and greater risks of systemic disease. The review also highlights numerous genetic conditions associated with male infertility as well as emerging translational evidence of genitourinary birth defects and their impact on male infertility. Finally, parallels to the overall health of infertile women are presented. This review highlights the importance of a comprehensive health evaluation of men who present for an infertility assessment.

Study of expression of genes potentially responsible for reduced fitness in patients with myotonic dystrophy type 1 and identification of new biomarkers of testicular function

Myotonic dystrophy type 1 (DM1) is a multisystemic disorder caused by trinucleotide CTG expansion in DMPK gene, often affecting the neighboring genes. Endocrine system is involved, resulting in hypogonadism and reproductive abnormalities, but molecular mechanisms underlying the reduced fertility observed in DM1 are very complex and partially unknown. To better characterize these mechanisms, an analysis of sperm parameters and anti-Müllerian hormone (AMH) values was performed in 20 DM1 patients. About 50% of them showed hypoposia and azoospermia; the remaining, despite an adequate volume of ejaculate, had oligo-astheno-teratozoospermia. Interestingly, the lowest AMH levels better correlated with the main sperm alterations. The pattern of expression of DMPK, SIX5, and RSPH6A genes, evaluated by quantitative reverse transcription polymerase chain reaction, showed a substantial reduction of the expression in both peripheral blood and in seminal plasma of patients, compared to controls. An impairment of testis-specific RSPH6A protein expression and localization was observed in sperm protein extracts by WB analysis and in isolated spermatozoa by immunofluorescence. These results support the hypothesis that CTG expansion also affects the expression of neighboring genes and contributes to gonad defects observed in DM1, suggesting the possibility of using them as markers for normal fertility in humans.

Sexual dysfunction and male infertility

Infertility affects up to 12% of all men, and sexual dysfunction occurs frequently in men of reproductive age, causing infertility in some instances. In infertile men, hypoactive sexual desire and lack of sexual satisfaction are the most prevalent types of sexual dysfunction, ranging from 8.9% to 68.7%. Erectile dysfunction and/or premature ejaculation, evaluated with validated tools, have a prevalence of one in six infertile men, and orgasmic dysfunction has a prevalence of one in ten infertile men. In addition, infertile men can experience a heavy psychological burden. Infertility and its associated psychological concerns can underlie sexual dysfunction. Furthermore, general health perturbations can lead to male infertility and/or sexual dysfunction. Erectile dysfunction and male infertility are considered proxies for general health, the former underlying cardiovascular disorders and the latter cancerous and noncancerous conditions. The concept that erectile dysfunction in infertile men might be an early marker of poor general health is emerging. Finally, medications used for general health problems can cause sperm abnormalities and sexual dysfunction. The treatment of some causes of male infertility might improve semen quality and reverse infertility-related sexual dysfunction. In infertile men, an investigation of sexual, general, and psychological health status is advisable to improve reproductive problems and general health.

Gonadal failure is associated with visceral adiposity in myotonic dystrophies

BACKGROUND

Hypogonadism occurs in myotonic dystrophies type 1 (MD1) and type 2 (MD2). Sertoli and Leydig cell secretions, including insulin-like peptide-3 (INSL3), anti-Müllerian hormone (AMH) and inhibin B, were evaluated in male patients with MD.

DESIGN

Academic settings. Forty-four male patients with MD [31 MD1, 13 MD2, aged 59 (50-64) years, median (interquartile range)], age-, sex- and BMI-matched non-MD hypogonadal patients (n = 14) and healthy controls (n = 32). Serum FSH, LH, inhibin B, AMH, testosterone (T) and INSL3 were measured; fat and muscle masses were evaluated by DEXA.

RESULTS

Overt primary hypogonadism occurred in 29% of patients with MD1 and 46% of patients with MD2. Considering subclinical forms, the prevalence increased to 69% of MD1 and 100% of MD2. A half of patients with MD experienced symptoms. INSL3 levels were unaffected in most patients with MD. By contrast, AMH and inhibin B were reduced in most patients with MD and unrelated to age. Patients with MD showed increased body and visceral fat. Free T levels were negatively predicted by fat mass, and AMH and FSH levels were negatively correlated with waist/hip ratio and fat mass. AMH, inhibin B and FSH levels positively correlated with muscle strength and muscle mass.

CONCLUSIONS

AMH and inhibin B secretion failures are common in male patients with MD and are more severe than Leydig cell hormones impairment. AMH and inhibin B measurements might provide clinical utility in evaluating fertility in patients with MD. Serum T, AMH and inhibin B productions are negatively influenced by increased fat mass, while AMH and inhibin B might be markers of muscle impairment.