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Microphallus Workup

  • Author: Karen S Vogt, MD; Chief Editor: Stephen Kemp, MD, PhD  more...
 
Updated: Jun 23, 2016
 

Laboratory Studies

A karyotype is recommended to confirm chromosomal sex. If PWS is suspected, methylation studies should be performed, and if positive, further genetic analysis for the specific genetic defect is indicated.

Gonadotropins (LH and FSH) reach pubertal levels in healthy male infants, peaking at age 1-3 months and declining by about age 6 months. Excessively high or low values during this "minipuberty" help to narrow the differential diagnoses.

Anti-M ü llerian hormone (M ü llerian inhibitory substance) and inhibin B are markers of Sertoli cell function and can be useful as indicators of the presence of testicular tissue in the setting of bilateral cryptorchidism.

Testosterone and DHT levels, before and after hCG stimulation, can be measured to evaluate the responsiveness of the testes to gonadotropin stimulation and for 5-alpha reductase deficiency (indicated by an increased testosterone-to-DHT ratio).

Given the possibility of panhypopituitarism, observe all infants with micropenis for hypoglycemia and evidence of other metabolic derangements. If hypoglycemia occurs, obtain a critical sample immediately before intravenous glucose is administered. The critical sample should include glucose, insulin, growth hormone, and cortisol levels.

In infants with hypoglycemia or suspected hypopituitarism, other pituitary hormone function should be evaluated. Evaluation of the thyroid axis should include measurement of total or free thyroxine (T4) as well as thyrotropin stimulating hormone (TSH). Growth hormone and cortisol levels may need to be measured after stimulation (eg, with glucagon for growth hormone and cortisol or ACTH for cortisol).

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Imaging Studies

In situations of genital ambiguity, pelvic ultrasonography is often helpful. The presence of a uterus and ovaries strongly suggests a virilized female (46,XX) infant.

When hypopituitarism is suspected, an MRI of the head should be obtained to evaluate the hypothalamic and pituitary areas. In Kallmann syndrome, abnormalities of the olfactory system may be seen.

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Other Tests

Testosterone therapy (testosterone enanthate or cypionate) 25 mg every month for 3 months has diagnostic and therapeutic implications. No appreciable increase in penis size (< 0.9 cm) with androgen therapy suggests androgen insensitivity.[10]

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Contributor Information and Disclosures
Author

Karen S Vogt, MD Pediatric Endocrinologist, Department of Pediatrics, Division of Endocrinology, Walter Reed National Military Medical Center

Karen S Vogt, MD is a member of the following medical societies: American Academy of Pediatrics, American Diabetes Association, Endocrine Society, Pediatric Endocrine Society

Disclosure: Nothing to disclose.

Coauthor(s)

Michael J Bourgeois, MD Director of Pediatric Undergraduate Medical Education, Associate Professor, Department of Pediatrics, Division of Pediatric Endocrinology and Metabolism, Texas Tech University School of Medicine

Michael J Bourgeois, MD is a member of the following medical societies: American Academy of Pediatrics, American Diabetes Association, Texas Medical Association

Disclosure: Nothing to disclose.

Specialty Editor Board

Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

George P Chrousos, MD, FAAP, MACP, MACE, FRCP(London) Professor and Chair, First Department of Pediatrics, Athens University Medical School, Aghia Sophia Children's Hospital, Greece; UNESCO Chair on Adolescent Health Care, University of Athens, Greece

George P Chrousos, MD, FAAP, MACP, MACE, FRCP(London) is a member of the following medical societies: American Academy of Pediatrics, American College of Physicians, American Pediatric Society, American Society for Clinical Investigation, Association of American Physicians, Endocrine Society, Pediatric Endocrine Society, Society for Pediatric Research, American College of Endocrinology

Disclosure: Nothing to disclose.

Chief Editor

Stephen Kemp, MD, PhD Former Professor, Department of Pediatrics, Section of Pediatric Endocrinology, University of Arkansas for Medical Sciences College of Medicine, Arkansas Children's Hospital

Stephen Kemp, MD, PhD is a member of the following medical societies: American Academy of Pediatrics, American Association of Clinical Endocrinologists, American Pediatric Society, Endocrine Society, Phi Beta Kappa, Southern Medical Association, Southern Society for Pediatric Research

Disclosure: Nothing to disclose.

Additional Contributors

Arlan L Rosenbloom, MD Adjunct Distinguished Service Professor Emeritus of Pediatrics, University of Florida College of Medicine; Fellow of the American Academy of Pediatrics; Fellow of the American College of Epidemiology

Arlan L Rosenbloom, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Epidemiology, American Pediatric Society, Endocrine Society, Pediatric Endocrine Society, Society for Pediatric Research, Florida Chapter of The American Academy of Pediatrics, Florida Pediatric Society, International Society for Pediatric and Adolescent Diabetes

Disclosure: Nothing to disclose.

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