Suspicion, screening, and diagnosis of wild-type transthyretin amyloid cardiomyopathy: a systematic literature review.

Wild-type transthyretin amyloid cardiomyopathy (ATTRwt CM) is a more common disease than previously thought. Awareness of ATTRwt CM and its diagnosis has been challenged by its unspecific and widely distributed clinical manifestations and traditionally invasive diagnostic tools. Recent advances in echocardiography and cardiac magnetic resonance (CMR), non-invasive diagnosis by bone scintigraphy, and the development of disease-modifying treatments have resulted in an increased interest, reflected in multiple publications especially during the last decade. To get an overview of the scientific knowledge and gaps related to patient entry, suspicion, diagnosis, and systematic screening of ATTRwt CM, we developed a framework to systematically map the available evidence of (i) when to suspect ATTRwt CM in a patient, (ii) how to diagnose the disease, and (iii) which at-risk populations to screen for ATTRwt CM. Articles published between 2010 and August 2021 containing part of or a full diagnostic pathway for ATTRwt CM were included. From these articles, data for patient entry, suspicion, diagnosis, and screening were extracted, as were key study design and results from the original studies referred to. A total of 50 articles met the inclusion criteria. Of these, five were position statements from academic societies, while one was a clinical guideline. Three articles discussed the importance of primary care providers in terms of patient entry, while the remaining articles had the cardiovascular setting as point of departure. The most frequently mentioned suspicion criteria were ventricular wall thickening (44/50), carpal tunnel syndrome (42/50), and late gadolinium enhancement on CMR (43/50). Diagnostic pathways varied slightly, but most included bone scintigraphy, exclusion of light-chain amyloidosis, and the possibility of doing a biopsy. Systematic screening was mentioned in 16 articles, 10 of which suggested specific at-risk populations for screening. The European Society of Cardiology recommends to screen patients with a wall thickness ≥12 mm and heart failure, aortic stenosis, or red flag symptoms, especially if they are >65 years. The underlying evidence was generally good for diagnosis, while significant gaps were identified for the relevance and mutual ranking of the different suspicion criteria and for systematic screening. Conclusively, patient entry was neglected in the reviewed literature. While multiple red flags were described, high-quality prospective studies designed to evaluate their suitability as suspicion criteria were lacking. An upcoming task lies in defining and evaluating at-risk populations for screening. All are steps needed to promote early detection and diagnosis of ATTRwt CM, a prerequisite for timely treatment.

Human testicular insulin-like factor 3 and endocrine disrupters.

The hormone insulin-like factor 3 (INSL3) is produced by testicular Leydig cells. Production of INSL3 is dependent on the state of Leydig cell differentiation and is stimulated by the long-term trophic effects of luteinizing hormone. INSL3 is, along with the other major Leydig cell hormone testosterone, essential for testicular descent, which in humans should be completed before birth. The incidence of cryptorchidism (incomplete descent of the testis) may have increased in some developed countries during recent decades. Experimental studies have shown that maternal exposure to endocrine-disrupting chemicals (EDCs), such as phthalates, can result in cryptorchidism among male offspring and that INSL3 production, like steroidogenesis, is susceptible to phthalate exposure. Inhibition of these hormones may occur via a general phthalate-induced impairment of Leydig cell development and maturation. Recent studies have also addressed the sensitivity of human Leydig cells to EDCs, though with varied conclusions.

Serum insulin-like factor 3 is highly correlated with intratesticular testosterone in normal men with acute, experimental gonadotropin deficiency stimulated with low-dose human chorionic gonadotropin: a randomized, controlled trial.

OBJECTIVE: To study the potential role for using serum biomarkers, including insulin-like factor 3 (INSL3), 17α-hydroxyprogesterone, antimüllerian hormone, and inhibin B, as correlates of intratesticular T (IT-T) concentrations in men. DESIGN: Prospective, randomized, controlled trial. SETTING: University-based medical center. PATIENT(S): Thirty-seven healthy men aged 18-50 years. INTERVENTION(S): All men received the GnRH antagonist acyline, plus very low doses of hCG (0 IU, 15 IU, 60 IU, or 125 IU) SC every other day or 7.5 g T gel daily (75 mg delivered). The IT-T concentrations obtained by percutaneous testicular aspiration with simultaneous serum protein and steroid concentrations were measured at baseline and after 10 days of treatment. MAIN OUTCOME MEASURE(S): Intratesticular and serum hormone and gonadotropin concentrations. RESULT(S): After 10 days of gonadotropin suppression, serum INSL3 decreased by more than 90% and correlated highly with IT-T concentrations. In contrast, serum inhibin B, antimüllerian hormone, and 17α-hydroxyprogesterone did not correlate with IT-T. Serum INSL3 increased with the dose of hCG administered and returned to baseline after treatment. CONCLUSION(S): Serum INSL3 correlates highly with IT-T and serum T concentrations during acute gonadotropin suppression in men. Human chorionic gonadotropin stimulates dose-dependent increases in INSL3 and IT-T in healthy men and might be a useful biomarker of IT-T concentration in some clinical settings. CLINICAL TRIAL REGISTRATION NUMBER: NCT# 00839319.

Testicular descent: INSL3, testosterone, genes and the intrauterine milieu.

Complete testicular descent is a sign of, and a prerequisite for, normal testicular function in adult life. The process of testis descent is dependent on gubernacular growth and reorganization, which is regulated by the Leydig cell hormones insulin-like peptide 3 (INSL3) and testosterone. Investigation of the role of INSL3 and its receptor, relaxin-family peptide receptor 2 (RXFP2), has contributed substantially to our understanding of the hormonal control of testicular descent. Cryptorchidism is a common congenital malformation, which is seen in 2-9% of newborn boys, and confers an increased risk of infertility and testicular cancer in adulthood. Although some cases of isolated cryptorchidism in humans can be ascribed to known genetic defects, such as mutations in INSL3 or RXFP2, the cause of cryptorchidism remains unknown in most patients. Several animal and human studies are currently underway to test the hypothesis that in utero factors, including environmental and maternal lifestyle factors, may be involved in the etiology of cryptorchidism. Overall, the etiology of isolated cryptorchidism seems to be complex and multifactorial, involving both genetic and nongenetic components.

Insulin-like factor 3 levels in second-trimester amniotic fluid.

BACKGROUND: According to animal studies, the testicular Leydig cell hormone insulin-like factor 3 (Insl3) exerts a fundamental role in abdominal testis translocation, which occurs in the beginning of the second trimester in humans. Despite this, human prenatal INSL3 production has been poorly investigated. METHODS: Amniotic fluid from 91 pregnant women undergoing amniocentesis was analyzed for INSL3 and testosterone (T) levels. Data were related to gestational age (15-25 wk) at amniocentesis and to sex (45 males and 48 females). RESULTS: INSL3 was present in amniotic fluid from all but one of the investigated male fetuses (range: <0.02-0.36 ng/ml; mean +/- sd: 0.12 +/- 0.07), whereas the hormone was undetectable in the female fetuses. T was significantly higher in male (range: 0.54-1.71 nmol/liter; mean +/- sd: 1.04 +/- 0.30) as compared with in female amniotic fluid (range: 0.19-0.50 nmol/liter; mean +/- sd: 0.34 +/- 0.06) (P < 0.001). In males there was no correlation between INSL3 and T. A statistically borderline negative association was found between INSL3 and gestational age (P = 0.07), whereas the corresponding association was not significant for T (P = 0.12). In contrast, T in females correlated positively with gestational age (P = 0.02). CONCLUSIONS: INSL3 is clearly present in human male amniotic fluid in the second trimester, where abdominal testis translocation takes place. In contrast, the hormone is undetectable in female amniotic fluid. The prenatal presence of INSL3 supports the hypothesis that this hormone is essential for testicular descent in humans.

Insulin-like factor 3 levels in cord blood and serum from children: effects of age, postnatal hypothalamic-pituitary-gonadal axis activation, and cryptorchidism.

CONTEXT: The Leydig cell hormone insulin-like factor 3 (INSL3) is important for testicular descent. Currently INSL3 levels in cord blood, in serum throughout childhood, and in relation to congenital cryptorchidism are unknown. OBJECTIVE: The objective of the study was to characterize INSL3 levels in cord blood during the postnatal activation of the hypothalamic-pituitary-gonadal axis and in later childhood in normal boys and girls and cryptorchid boys. DESIGN AND PARTICIPANTS: Serum from 267 3-month-old boys of a prospective study with standardized cryptorchidism classification was analyzed for INSL3 (of these, 99 also had cord blood samples). Testicular position was known in 151 controls and 54 transiently cryptorchid and 62 persistently cryptorchid subjects. Eight infant girls, 26 boys (4.1-10.1 yr), and 13 girls (3.7-8.7 yr) were also included. OUTCOME MEASURE: INSL3, age, testicular position, LH, and testosterone were measured. RESULTS: INSL3 levels were significantly higher (P < 0.001) in cord blood and 3-month-old boys as compared with older prepubertal boys. At 3 months of age, INSL3 correlated significantly with LH in healthy boys. Cord blood INSL3 was significantly reduced in persistently cryptorchid boys (P = 0.001), and 3-month-old persistently cryptorchid boys had a significantly increased LH to INSL3 ratio (P = 0.014). INSL3 was unmeasurable in girls at all ages. CONCLUSIONS: In boys, early postnatal INSL3 is markedly higher as compared with later childhood, presumably because it is stimulated by the transient postnatal LH peak. INSL3 was unmeasurable in girls at all ages. Reduced cord blood INSL3 and an increased LH to INSL3 ratio at 3 months of age in persistently cryptorchid boys suggest impaired Leydig cell function in cryptorchid boys already in the perinatal period.

Serum insulin-like factor 3 levels during puberty in healthy boys and boys with Klinefelter syndrome.

CONTEXT: Levels of the Leydig cell-specific hormone insulin-like factor 3 (INSL3) are incompletely characterized in boys during pubertal development. OBJECTIVE: The objective of the study was to characterize changes in INSL3 levels during spontaneous puberty in healthy boys, boys with aromatase inhibitor-induced hypergonadotropic hyperandrogenism, and boys with Leydig cell dysfunction. DESIGN: This was a prospective clinical study. SETTING: The study was conducted at a university hospital pediatric endocrinology outpatient clinic. PATIENTS: Patients included 30 healthy boys with idiopathic short stature (ISS) aged 9.0-14.5 yr and 14 boys with Klinefelter syndrome (KS) aged 10-13.9 yr. INTERVENTION: In ISS boys, intervention included aromatase inhibitor letrozole or placebo for 24 months. MAIN OUTCOME MEASURES: Serum INSL3 levels in relation to bone age, Tanner pubertal stages, and LH and testosterone levels were measured. RESULTS: Onset of puberty was associated with a significant increase in INSL3 levels from 0.06 +/- 0.01 ng/ml at Tanner G1 to 0.32 +/- 0.16 ng/ml at G2 (P < 0.0001). Adult INSL3 levels (> or = 0.55 ng/ml) were attained at bone age 13-14 yr. ISS boys with letrozole-induced hypergonadotropic hyperandrogenism had, after 12 months of therapy, higher INSL3 levels than did placebo treated (0.85 +/- 0.54 vs. 0.26 +/- 0.17 ng/ml, P < 0.01). In KS boys during spontaneous puberty, after an initial increase similar to that in healthy boys, INSL3 concentrations leveled off despite hyperstimulation by LH. Positive correlations occurred between serum INSL3 and LH and between INSL3 and testosterone levels in all three groups (P < 0.0001). CONCLUSIONS: In boys, the Leydig cell-specific hormone INSL3 may serve as a new marker for onset and progression of puberty. Pubertal increase in INSL3 levels seems to depend on LH. In KS subjects, INSL3 concentrations indicate Leydig cell dysfunction from midpuberty onward.

Testicular dysgenesis syndrome: possible role of endocrine disrupters.

The testicular dysgenesis syndrome (TDS) hypothesis proposes that the four conditions cryptorchidism, hypospadias, impaired spermatogenesis and testis cancer may all be manifestations of disturbed prenatal testicular development. The TDS hypothesis is based on epidemiological, clinical and molecular studies, all suggestive of an interrelation between the different symptoms. The aetiology of TDS is suspected to be related to genetic and/or environmental factors, including endocrine disrupters. Few human studies have found associations/correlations between endocrine disrupters, including phthalates, and the different TDS components. However, for ethical reasons, evidence of a causal relationship between prenatal exposure and TDS is inherently difficult to establish in human studies, rendering the recently developed animal TDS model an important tool for investigating the pathogenesis of TDS. Clinically, the most common manifestation of TDS is probably a reduced sperm concentration, whereas the more severe form may include a high risk of testis cancer. Clinicians should be aware of the interconnection between the different features of TDS, and inclusion of a programme for early detection of testis cancer in the management of infertile men with poor semen quality is recommended.

The effects of gonadotropin suppression and selective replacement on insulin-like factor 3 secretion in normal adult men.

CONTEXT: Gonadotropic regulation of the testicular Leydig cell hormone insulin-like factor 3 (INSL3) is incompletely characterized. OBJECTIVE: The objective of this study was to assess the effects of gonadotropin suppression and induced or spontaneous recovery on serum INSL3. DESIGN AND PARTICIPANTS: Serum samples from 15 men enrolled in a short-term study of gonadotropin stimulation, suppression, and recovery and 11 men in a long-term study of gonadotropin suppression and spontaneous recovery were analyzed for INSL3. INTERVENTION: Gonadotropins were suppressed by exogenous testosterone and progestin. Recovery was spontaneous or induced with exogenous gonadotropins. OUTCOME MEASURE: The outcome measure was serum INSL3 in relation to other reproductive hormones. RESULTS: Serum INSL3 was not acutely sensitive to gonadotropins. In both studies, INSL3 declined markedly with gonadotropin suppression (6-13.5% of baseline; P < 0.05). In the short-term study, human chorionic gonadotropin partially restored suppressed serum INSL3 within 4 d of administration (from 7.5 to 38.3% baseline; P < 0.05); the increase correlated with the corresponding increase in serum pro-alphaC (r = 0.82; P < 0.01). FSH did not stimulate the suppressed INSL3. In the long-term study, serum testosterone recovered significantly better (80% baseline) compared with serum INSL3 (38.9% baseline; P < 0.01) in the presence of fully recovered serum LH. CONCLUSIONS: INSL3 is not sensitive to gonadotropin stimulation in normal men, but declines markedly in response to gonadotropin deprivation. After suppression, INSL3 was responsive to hCG 4 d after administration. After long-term suppression, INSL3 did not recover to the same degree as testosterone, suggesting that INSL3 is more sensitive to Leydig cell impairment than testosterone.

Estradiol levels in prepubertal boys and girls--analytical challenges.

Increasing evidence points at an important function of low concentrations of estradiol (E2) in prepubertal boys and girls. E2 serum levels in prepubertal children are, however, often immeasurable in conventional E2 assays. This strongly hampers further investigation of the physiological relevance of E2 in children. In addition, there is an increasing concern of the potential effect of exposure to endocrine disrupters with estrogenic or antiandrogenic activity on pubertal development. A requirement of assessing the instance for this concern, adds further to the demands for applicable methodologies for the evaluation of the sensitivity of the organism to low E2 concentrations. Traditionally, E2 is measured by use of the radioimmunoassay (RIA). As an ultrasensitive alternative to the RIA, a recombinant cell bioassay has been developed. In this review, methodological aspects for these methods of analysis are examined and their applicability for evaluation of low E2 serum concentrations in children is estimated. Furthermore, available data on E2 levels in prepubertal boys and girls are evaluated and discussed, taking into consideration the limitations of the methods of analysis. In conclusion, there is a pronounced demand for new and improved methods of analysis for accurate and sensitive evaluation of low concentrations of E2.