Micropenis: adult follow-up and comparison of size against new norms

Worldwide Temporal Trends in Penile Length: A Systematic Review and Meta-Analysis

PURPOSE

Normative male genital measurements are clinically useful and temporal changes would have important implications. The aim of the present study is to characterize the trend of worldwide penile length over time.

MATERIALS AND METHODS

A systematic review and meta-analysis using papers from PubMed, Embase, and Cochrane Library from inception to April 2022 was performed. PRISMA guidelines were used for abstracting data and assessing data quality and validity. Pooled means and standard deviations for flaccid, stretched, and erect length were obtained. Subgroup analyses were performed by looking at differences in the region of origin, population type, and the decade of publication. Metaregression analyses were to adjusted for potential confounders.

RESULTS

Seventy-five studies published between 1942 and 2021 were evaluated including data from 55,761 men. The pooled mean length estimates were flaccid length: 8.70 cm (95% CI, 8.16-9.23), stretched length: 12.93 cm (95% CI, 12.48-13.39), and erect length: 13.93 cm (95% CI, 13.20-14.65). All measurements showed variation by geographic region. Erect length increased significantly over time (QM=4.49, df=2, p=0.04) in several regions of the world and across all age groups, while no trends were identified in other penile size measurements. After adjusting for geographic region, subject age, and subject population; erect penile length increased 24% over the past 29 years.

CONCLUSIONS

The average erect penis length has increased over the past three decades across the world. Given the significant implications, attention to potential causes should be investigated.

Congenital Micropenis: Etiology And Management

In the newborn, penile length is determined by a number of androgen dependent and independent factors. The current literature suggests that there are interracial differences in stretched penile length in the newborn and although congenital micropenis should be defined as a stretched penile length of less than 2.5 SDS of the mean for the corresponding population and gestation, a pragmatic approach would be to evaluate all boys with a stretched penile length below 2 cm, as congenital micropenis can be a marker for a wide range of endocrine conditions. However, it remains unclear as to whether the state of micropenis, itself, is associated with any long-term consequences. There is a lack of systematic studies comparing the impact of different therapeutic options on long-term outcomes, in terms of genital appearance, quality of life, and sexual satisfaction. To date, research has been hampered by a small sample size and inclusion of a wide range of heterogeneous diagnoses; for these reasons, condition-specific outcomes have been difficult to compare between studies. Lastly, there is a need for a greater collaborative effort in collecting standardized data so that all real-world or experimental interventions performed at an early age can be studied systematically into adulthood.

'Idiopathic' partial androgen insensitivity syndrome in 28 newborn and infant males: impact of prenatal exposure to environmental endocrine disruptor chemicals?

OBJECTIVE

46,XY disorders of sex differentiation (46,XY DSD) can be due to a testis determination defect, an androgen biosynthesis defect, or androgen resistance (complete or partial androgen insensitivity syndrome (PAIS), or 5α reductase deficiency). We aimed to evaluate the impact of a prenatal contamination by environmental xenoestrogens in 'idiopathic' PAIS-like phenotype.

SUBJECTS

We investigated 28 newborn/infant males with 46,XY DSD, normal androgen production, and no androgen receptor or steroid-5αR type II enzyme (SRD5A2) gene mutations.

METHODS

To exclude other genetic defects, we sequenced the steroidogenic factor 1 (SF1) and mastermind-like domain-containing 1 (MAMLD1) genes, which were recently found to be associated with the PAIS-like phenotype. Parents were interviewed about their environmental/occupational exposure to endocrine disrupting chemicals (EDCs) before/during the patients' fetal life. Total estrogenic bioactivity of patient serum was analyzed by ultrasensitive bioassay.

RESULTS

All the patients had normal SF1 sequence and one patient showed a double polymorphism of MAMLD1. Eleven (39.3%) of the 28 patients had reported parental fetal exposure to EDCs. The mean estrogenic bioactivity in these 11 patients with fetal EDC exposure (6.65 ± 8.07 pg/ml) versus 17 cases without contamination (1.27 ± 0.34 pg/ml) and controls (1.06 ± 0.44 pg/ml; P<0.05) was elevated.

CONCLUSIONS

Our results indicate that the 'idiopathic' PAIS-like phenotype may in some cases be related to EDC contamination during fetal life.

Prenatal environmental risk factors for genital malformations in a population of 1442 French male newborns: a nested case-control study

BACKGROUND

Over the past decades, an increasing trend in male external genital malformations such as cryptorchidism and hypospadias has led to the suspicion that environmental chemicals are detrimental to male fetal sexual development. Several environmental pollutants, including organochlorine pesticides, polychlorinated biphenyls, bisphenol A, phthalates, dioxins and furans have estrogenic and anti-androgenic activity and are thus considered as endocrine-disrupting chemicals (EDCs). Since male sex differentiation is critically dependent on the normal production and action of androgens during fetal life, EDCs may be able to alter normal male sex differentiation.

OBJECTIVE

The objective of this study was to determine the incidence of external genital malformations in a population of full-term newborn males in southern France. We also performed a case-control study to identify the risk factors for male external genital malformations, with a focus on parental occupational exposure to EDCs.

METHODS

Over a 16-month period, 1615 full-term newborn males with a birth weight above 2500 g were registered on a level-1 maternity ward, and the same pediatrician systematically examined 1442 of them (89%) for cryptorchidism, hypospadias and micropenis. For every male newborn with genital malformation, we enrolled nearly two males matched for age, parity and term. All parents of the case and control newborns were interviewed about pregnancy aspects, personal characteristics, lifestyle and their occupational exposure to EDCs using a detailed questionnaire. RESULTS We report 39 cases of genital malformation (2.70%), with 18 cases of cryptorchidism (1.25%), 14 of hypospadias (0.97%), 5 of micropenis (0.35%) and 2 of 46,XY disorders of sexual differentiation (DSD; 0.14%). We observed a significant relationship between newborn cryptorchidism, hypospadias or micropenis and parental occupational exposure to pesticides [odds ratio (OR) = 4.41; 95% confidence interval (95% CI), 1.21-16.00]. Familial clustering for male external genital malformations (OR = 7.25; 95% CI, 0.70-74.30) and medications taken by mothers during pregnancy (OR = 5.87; 95% CI, 0.93-37.00) were associated with the risk of cryptorchidism, hypospadias and micropenis, although the association was not statistically significant.

CONCLUSIONS

Although the causes of male genital malformation are multifactorial, our data support the hypothesis that prenatal contamination by pesticides may be a potential risk factor for newborn male external genital malformation and it should thus be routinely investigated in all undervirilized newborn males.

The androgen insensitive micropenis: long-term follow-up into adulthood

AIM

To assess the adult stretched penile length (SPL) and sexuality in patients with micropenis who exhibited an inadequate response to exogenous testosterone therapy and were raised as males.

PATIENTS AND METHODS

Patients with micropenis who had an equivocal response to exogenous testosterone therapy and were raised as males were evaluated at adulthood (>17 yr).

RESULTS AND CONCLUSIONS

Twenty patients with micropenis, initial median SPL -3.3 SD below the mean (range -5.5 to -2.6) had a suboptimal response to initial testosterone therapy, median SPL post-treatment -2.7 SD (-3.3 to -2.2), and were raised as males. At adulthood, 90% (18/20) had a micropenis, median SPL -3.4 (-5.9 to -2.2). All have a male gender identity, five are undergoing psychiatric counseling (fear of sexual rejection--five patients, one of whom also has suicidal ideation). Eight have not pursued a sexual relationship; 12 are sexually active, one of whom is bisexual.

Outcome studies among men with micropenis

Adult stretched penile length (SPL) was determined among 22 males who were diagnosed with micropenis. These adult SPL values were compared with SPL at the time of diagnosis, age of diagnosis and etiologic category in 20 men who were diagnosed before puberty. A portion of this group completed a structured questionnaire interview, the Social Adjustment Self Report Questionnaire and the Hopkins Symptom Checklist to assess social and psychosexual milestones and the presence of psychiatric morbidity. Results show that the majority of men who had been diagnosed with micropenis had an adult SPL within 2 standard deviations of the normal adult mean, with only a minority showing values below this. It appeared that men with micropenis might have greater than average interval SPL growth between diagnosis and adulthood; it remains unclear whether this supranormal growth represents a catch-up phenomenon or results from augmentation by intermittent androgen therapy. There was no clear relationship between SPL at diagnosis and SPL in adulthood. The responses to the questionnaires indicated that men who had been diagnosed with micropenis were comparable to control men in regard to gender issues, body image, social fitness, sexuality, work, family adjustment and the presence of psychopathology.

Ambiguous genitalia with perineoscrotal hypospadias in 46,XY individuals: long-term medical, surgical, and psychosexual outcome

OBJECTIVES

To identify and study adults (21 years or older) who have a 46,XY karyotype and presented as infants or children with genital ambiguity, including a small phallus and perineoscrotal hypospadias, reared male or female.

METHODS

Participants were classified according to the cause underlying their intersex condition based on review of medical and surgical records. Long-term medical and surgical outcome was assessed with a written questionnaire and physical examination. Long-term psychosexual development was assessed with a written questionnaire and semistructured interview.

RESULTS

Thirty-nine (72%) of 54 eligible patients participated. The cause underlying genital ambiguity of participants included partial androgen insensitivity syndrome (n = 14; 5 men and 9 women), partial gonadal dysgenesis (n = 11; 7 men and 4 women), and other intersex conditions. Men had significantly more genital surgeries (mean: 5.8) than women (mean: 2.1), and physician-rated cosmetic appearance of the genitalia was significantly worse for men than for women. The majority of participants were satisfied with their body image, and men and women did not differ on this measure. Most men (90%) and women (83%) had sexual experience with a partner. Men and women did not differ in their satisfaction with their sexual function. The majority of participants were exclusively heterosexual, and men considered themselves to be masculine and women considered themselves to be feminine. Finally, 23% of participants (5 men and 4 women) were dissatisfied with their sex of rearing determined by their parents and physicians.

CONCLUSIONS

Either male or female sex of rearing can lead to successful long-term outcome for the majority of cases of severe genital ambiguity in 46,XY individuals. We discuss factors that should be considered by parents and physicians when deciding on a sex of rearing for such infants.

Etiology, clinical profile, gender identity and long-term follow up of patients with ambiguous genitalia in India

There is little information on the profile of children with ambiguous genitalia in India. Presented here is an analysis of patients with ambiguous genitalia registered in a general endocrine clinic during the last 2 decades. Seventy-four patients (age 4 months to 36 years) were registered during this period. Fifty-two were more than 5 years old at the time of registration. Thirty-five were reared as females, 29 as males; nine children (4 months to 1 year old) were brought for sex assignment, and one (with epispadias) was brought for correction of urinary incontinence. Investigations revealed 28 patients with congenital adrenal hyperplasia, 14 dysgenetic male pseudohermaphroditism, ten true hermaphroditism, six partial androgen insensitivity, four castration and one epispadias. There were eight patients with perineal hypospadias with normal Leydig cell reserve (normal LH, FSH and testosterone response to LHRH). Sex of rearing and gender identity were concordant in all except the patients with perineal hypospadias with normal Leydig cell response. These observations support the theory that prenatal androgen exposure masculinizes the brain.

Congenital hypogonadotropic hypogonadism and micropenis: effect of testosterone treatment on adult penile size why sex reversal is not indicated

Micropenis is commonly due to fetal testosterone deficiency. The clinical management of this form of micropenis has been contentious, with disagreement about the capacity of testosterone treatment to induce a functionally adequate adult penis. As a consequence, some clinicians recommend sex reversal of affected male infants. We studied 8 male subjects with micropenis secondary to congenital pituitary gonadotropin deficiency from infancy or childhood to maturity (ages 18 to 27 years). Four patients were treated with testosterone before 2 years of age (group I) and four between age 6 and 13 years (group II). At presentation, the mean penile length in group I was 1.1 cm (-4 SD; range, 0.5 to 1.5 cm) and in group II it was 2.7 cm (-3.4 SD; range, 1.5 to 3.5 cm). All patients received one or more courses of 3 intramuscular injections of testosterone enanthate (25 or 50 mg) at 4-week intervals in infancy or childhood. At the age of puberty the dose was gradually increased to 200 mg monthly and later to an adult replacement regimen. As adults, both group I and II had attained a mean final penile length of 10.3 cm 2.7 cm with a range of 8 to 14 cm (mean adult stretched penile length for Caucasians is 12.4 2.7 cm). Six of 8 men were sexually active, and all reported normal male gender identity and psychosocial behavior. We conclude that 1 or 2 short courses of testosterone therapy in infancy and childhood augment penile size into the normal range for age in boys with micropenis secondary to fetal testosterone deficiency; replacement therapy at the age of puberty results in an adult size penis within 2 SD of the mean. We found no clinical, psychologic, or physiologic indications to support conversion of affected male infants to girls. Further, the results of this study do not support the notion, derived from data in the rat, that testosterone treatment in infancy or childhood impairs penile growth in adolescence and compromises adult penile length.

The effects of androgen administration on phallic androgen receptor expression

PURPOSE

Whether androgens down regulate the androgen receptor during penile development is controversial. We investigated the effects of androgens on penile androgen receptor expression.

MATERIALS AND METHODS

We injected prepubertal hypogonadotropic hypogonadal microphallic rats with testosterone or dihydrotestosterone. Specimens were obtained at 3 (prepuberty), 9 (puberty to early postpuberty) and 12 weeks (late postpuberty). At necropsy we compared penile size and androgen receptor expression of these animals to those of age matched nontreated hypogonadotropic hypogonadal and normal controls.

RESULTS

At age 3 weeks prepubertal androgens up regulated androgen receptor expression and significantly increased penile size compared to normal and untreated hypogonadotropic hypogonadal controls. By 9 weeks the normal down regulation of androgen receptor that occurs with maturation was present. Prepubertal androgens failed to accelerate or exaggerate the normal maturational loss of the androgen receptor. At 9 weeks penile size of normal controls and prepubertal androgen treated animals was identical. Interestingly despite down regulation of the penile androgen receptor, normal animals continued to have increases in penile size between 9 and 12 weeks, while the prepubertal androgen treated animals had no penile growth.

CONCLUSIONS

Prepubertal androgen administration in hypogonadotropic hypogonadal animals resulted in diminutive penises in adulthood. However, the decrease in penile size was not associated with an accelerated or exaggerated down regulation of the androgen receptor. This finding coupled with continued growth of the normal control penises after androgen receptor down regulation suggests that cessation of penile growth may not be solely related to down regulation of the penile androgen receptor.

Microphallus: eventual phallic size is dependent on the timing of androgen administration

Micropenis secondary to hypogonadotropic hypogonadism in the Sprague-Dawley rat was induced by either injection of supraphysiological doses of dihydrotestosterone to the timed pregnant dam on gestational days 16 and 17 or by long acting microspheres of the gonadotropic agonist, leuprolide acetate. Following the induction of micropenis the animals were treated with dihydrotestosterone beginning at either day 7, 28, 56 or 84 of life. Within the study populations all animals treated with dihydrotestosterone had phallic enlargement greater than untreated controls (p < 0.01). However, animals beginning treatment on day 7 or 28 had persistent microphallus (p < 0.01). In contrast, if hormonal therapy was initiated on day 56 or 84 the phallus became normal in length. Immunohistological studies for androgen receptor expression revealed that early androgen exposure accelerated the loss of androgen receptor protein from the penis during growth. These data suggest that prepubertal exposure of the penis to androgens may significantly reduce the eventual penile size of the hypogonadotropic hypogonadal micropenis.