Erik Knauff - Academia.edu (original) (raw)

Papers by Erik Knauff

Context: Ovarian dysfunction is classically categorized on the basis of cycle history, FSH, and e... more Context: Ovarian dysfunction is classically categorized on the basis of cycle history, FSH, and estradiol levels. Novel ovarian markers may provide a more direct insight into follicular quantity in hypergonadotropic women. Objective: The objective of the study was to investigate the distribution of novel ovarian markers in young hypergonadotropic women as compared with normogonadotropic regularly menstruating women. Design: This was a nationwide prospective cohort study. Setting: The study was conducted at 10 hospitals in The Netherlands. Patients: Women below age 40 yr with regular menses and normal FSH (controls; n ϭ 83), regular menstrual cycles and elevated FSH [incipient ovarian failure (IOF); n ϭ 68]; oligomenorrhea and elevated FSH [referred to as transitional ovarian failure (TOF); n ϭ 79]; or at least 4 months amenorrhea together with FSH levels exceeding 40 IU/liter [premature ovarian failure (POF); n ϭ 112]. Main Outcome Measures: Serum levels of anti-Mü llerian hormone (AMH), inhibin B, and antral follicle count (AFC) was measured. Results: All POF patients showed AMH levels below the fifth percentile (p 5) of normoovulatory women. Normal AMH levels (Ͼp 5) could be identified in 75% of IOF, 33% of TOF patients, and 98% of controls. AFC and AMH levels changed with increasing age (P Ͻ 0.0001), whereas inhibin B did not (P ϭ 0.26). AMH levels were significantly different between TOF and IOF over the entire age range, whereas AFC became similar for TOF and IOF at higher ages. Conclusions: Compared with inhibin B and AFC, AMH was more consistently correlated with the clinical degree of follicle pool depletion in young women presenting with elevated FSH levels. AMH may provide a more accurate assessment of the follicle pool in young hypergonadotropic patients, especially in the clinically challenging subgroups of patients with elevated FSH and regular menses (i.e. IOF) and in hypergonadotropic women with cycle disturbances not fulfilling the POF diagnostic criteria (i.e. TOF).

Menopause (New York, N.Y.)

Earlier menopause is associated with a higher incidence of cardiovascular events later in life. C... more Earlier menopause is associated with a higher incidence of cardiovascular events later in life. Concurrent with the ages of menopausal transition, a shift in lipid profile takes place. Premature ovarian failure (POF) or premature menopause allows us to study the effect of cessation of ovarian function on the lipid profile independent of effects of advanced chronological age. Fasting triglycerides (TGs), total high-density lipoprotein (HDL), and low-density lipoprotein cholesterol levels were measured in 90 women with POF not using any hormone therapy and 198 population controls of the same age range not using oral contraceptives. Correlations between lipids and ovarian function parameters were assessed. : After correction for age, body mass index, and smoking, women with POF presented with significantly higher TG levels (mean difference: 0.17 log mmol/L [95% CI: 0.06-0.29]). HDL cholesterol levels were borderline significantly lower in women with POF. No age-corrected correlation be...

Trends in Endocrinology & Metabolism, 2007

Over the past few decades, postponement of childbearing has led to a decrease in family size and ... more Over the past few decades, postponement of childbearing has led to a decrease in family size and increased rates of age-related female subfertility. Age-related decrease in ovarian follicle numbers and a decay in oocyte quality dictate the occurrence of natural loss of fecundity and, ultimately, menopause. The rate of this ovarian ageing process is highly variable among women. Identification of women who have severely decreased ovarian reserve for their age is, therefore, clinically relevant. Endocrine and imaging tests for ovarian reserve relate mainly to the quantitative aspect of ovarian reserve, but their capacity to predict the chances for pregnancy is limited. Genetic factors regulating the size of the follicle pool and the rate of its depletion might be identified in the near future and, possibly, assist the accurate prediction of a woman's reproductive lifespan.

Reproductive Sciences, 2007

Female patients with classical galactosemia (galactose-1-phosphate uridyltransferase [GALT] defic... more Female patients with classical galactosemia (galactose-1-phosphate uridyltransferase [GALT] deficiency) frequently suffer from premature ovarian failure, despite treatment with a galactose-restricted diet. Earlier research has suggested an association between heterozygosity for GALT mutations and early menopause. This study evaluates the effect of carriership for classical galactosemia on ovarian reserve and menopausal age. Proven female carriers of classical galactosemia were recruited via the Dutch Galactosemia Society. All 58 participants underwent a structured interview regarding fertility, smoking status, and menopause. To determine ovarian reserve, 42 premenopausal GALT carriers underwent ovarian antral follicle count (AFC) by transvaginal ultrasound and early follicular phase blood sampling for hormonal measurement of follicle-stimulating hormone (FSH), inhibin B, and anti-Müllerian hormone (AMH). These ovarian reserve parameters were compared with a cohort of proven fertile women (n = 166). The mean age at menopause in GALT carriers was 49.7 years, which is not different from the mean age at menopause in the general population in the Netherlands. There was no difference in FSH, inhibin B, and AMH levels or in the AFC (when corrected for age and smoking status) between 42 premenopausal GALT carriers and controls. The authors conclude that there is no evidence that GALT mutation carriership affects ovarian reserve or menopausal age.

Menopause, 2010

Premature ovarian failure (POF) is characterized by secondary amenorrhea before the age of 40 yea... more Premature ovarian failure (POF) is characterized by secondary amenorrhea before the age of 40 years, along with repeated increased follicle-stimulating hormone and low estrogen concentrations. POF is considered a complex genetic disease with a familial presentation in 12% to 50% of cases. POF may originate from different genes and various gene-environment interactions. The aim of this study was to identify possible differences in phenotype comparing women with familial and women with sporadic POF. A multicenter study was initiated in the Netherlands using standardized phenotyping. For each woman, medical history, menstrual cycle, and fertility and smoking status were assessed and a standardized examination was performed. Based on a detailed three-generation family history, women were identified as having either familial (defined as having at least one relative with POF) or sporadic POF. A total of 58 familial cases and 142 sporadic cases of POF were identified. Maternal age at menopause was significantly lower in the women with familial compared with the women with sporadic POF (41.0 +/- 7.5 and 49.7 +/- 2.6 y, respectively; P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001). Sex hormone-binding globulin concentration was significantly higher in the women with familial than in the women with sporadic POF (73.6 +/- 37.1 and 55.2 +/- 26.9 nmol/L, respectively; P = 0.002). All other characteristics, such as parity, bone mineral density, and serum follicle-stimulating hormone and lipid levels were similar, as was the incidence of autoimmunity and cytogenetic abnormalities. Familial and sporadic POF do not differ in phenotype except for maternal menopause age and sex hormone-binding globulin concentration. Future studies are needed to unravel the genotype-phenotype interactions in POF.

The Journal of Clinical Endocrinology & Metabolism, 2009

Human Reproduction, 2008

Polycystic ovary syndrome (PCOS) is associated with metabolic abnormalities. It is debated whethe... more Polycystic ovary syndrome (PCOS) is associated with metabolic abnormalities. It is debated whether all women with PCOS should be screened for metabolic abnormalities as these may vary with PCOS phenotype, age and ethnicity. The aims of this study were to assess the prevalence of metabolic abnormalities in Dutch anovulatory PCOS women and to define criteria for metabolic screening. methods: Anovulatory patients, diagnosed with PCOS according to the Rotterdam consensus criteria, underwent metabolic screening. Through stepwise multivariate analysis patient characteristics associated with metabolic syndrome (MetS) and insulin resistance (IR) were evaluated for their use as selection parameters for metabolic screening. results: Overall, prevalence of MetS and IR was 15.9% (n ¼ 25) and 14% (n ¼ 22), respectively, in 157 PCOS women (age 29.0 + 4.8 years, BMI 26.1 + 6.7 kg/m 2). Anovulatory hyperandrogenic women (with or without polycystic ovaries) had more often MetS and IR (with, 20.8 and 19.8%; without, 100 and 40%, respectively) than non-hyperandrogenic PCOS women (0 and 1.8%; P , 0.001). Waist circumference .83.5 cm along with increased free androgen index (FAI) had the most powerful association with the presence of MetS and IR (area under the receiver operating characteristic curve 0.912) and offered a reduction in the necessity of screening for metabolic derailments of about 50%. conclusions: The hyperandrogenic PCOS phenotypes are highly linked to the presence of MetS and IR in Dutch PCOS women. Waist circumference combined with FAI was identified as an efficient combination test to select those PCOS women who should be screened for the presence of MetS and/or IR.

Human Reproduction, 2009

background: Spontaneous premature ovarian failure (POF) occurs in 1% of women and has major impli... more background: Spontaneous premature ovarian failure (POF) occurs in 1% of women and has major implications for their fertility and health. Besides X chromosomal aberrations and fragile X premutations, no common genetic risk factor has so far been discovered in POF. Using high-density single nucleotide polymorphism (SNP) arrays, we set out to identify new genetic variants involved in this condition. methods: A genome-wide association study involving 309 158 SNPs was performed in 99 unrelated idiopathic Caucasian POF patients and 235 unrelated Caucasian female controls. A replication study on the most significant finding was performed. We specifically focused on chromosomal areas and candidate genes previously implicated in POF.

Fertility and Sterility, 2011

Objective: To investigate whether submicroscopic copy number variants (CNVs) on the X chromosome ... more Objective: To investigate whether submicroscopic copy number variants (CNVs) on the X chromosome can be identified in women with primary ovarian insufficiency (POI), defined as spontaneous secondary amenorrhea before 40 years of age accompanied by follicle-stimulating hormone levels above 40 IU/L on at least two occasions. Design: Analysis of intensity data of single nucleotide polymorphism (SNP) probes generated by genomewide Illumina 370k CNV BeadChips, followed by the validation of identified loci using a custom designed ultra-high-density comparative genomic hybridization array containing 48,325 probes evenly distributed over the X chromosome. Setting: Multicenter genetic cohort study in the Netherlands. Patient(s): 108 Dutch Caucasian women with POI, 97 of whom passed quality control, who had a normal karyogram and absent fragile X premutation, and 235 healthy Dutch Caucasian women as controls. Intervention(s): None. Main Outcome Measure(s): Amount and locus of X chromosomal microdeletions or duplications. Result(s): Intensity differences between SNP probes identify microdeletions and duplications. The initial analysis identified an overrepresentation of deletions in POI patients. Moreover, CNVs in two genes on the Xq21.3 locus (i.e., PCDH11X and TGIF2LX) were statistically significantly associated with the POI phenotype. Mean size of identified CNVs was 262 kb. However, in the validation study the identified putative Xq21.3 deletions samples did not show deviations in intensities in consecutive probes. Conclusion(s): X chromosomal submicroscopic CNVs do not play a major role in Caucasian POI patients. We provide guidelines on how submicroscopic cytogenetic POI research should be conducted.

Fertility and Sterility, 2013

Objective: To investigate the role of serum antim€ ullerian hormone (AMH) as a predictor of live ... more Objective: To investigate the role of serum antim€ ullerian hormone (AMH) as a predictor of live birth and reproductive stage in subfertile women with elevated basal FSH levels.

BJOG: An International Journal of Obstetrics & Gynaecology, 2006

Objective The current report aims to compare the prevalence of polycystic ovary syndrome (PCOS) ... more Objective The current report aims to compare the prevalence of polycystic ovary syndrome (PCOS) diagnosed according to the new Rotterdam criteria (Rott‐PCOS) versus the previous criteria as formulated by the National Institutes of Health (NIH) (NIH‐PCOS) in women with normogonadotropic (WHO‐II) anovulation and assess the frequency of obesity and related factors determined in these women.Design Cohort study based on large anovulation screening database.Setting Two large tertiary referral centres for reproductive medicine.Population WHO‐II normogonadotropic, anovulatory, infertility cases.Methods WHO‐II cases were extracted from the screening database and classified according to both the Rotterdam and NIH criteria for PCOS. Within these two classes, the prevalence of obesity, hyperglycaemia and insulin resistance was assessed and compared and their relation to the difference in diagnostic criteria applied was analysed.Main outcome measures Prevalence of diagnosis PCOS in the WHO...