eMedicine Specialties > Pediatrics: General Medicine > Endocrinology

Microphallus: Differential Diagnoses & Workup

Author: Karen S Vogt, MD, Pediatric Endocrinologist, Department of Pediatrics, Division of Endocrinology, Walter Reed Army Medical Center
Coauthor(s): Merrily P M Poth, MD, Professor, Department of Pediatrics and Neuroscience, Uniformed Services University of the Health Sciences; Andrew J Bauer, MD, Program Director, Department of Pediatrics, Division of Pediatric Endocrinology, Uniformed Services University of the Health Sciences; 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
Contributor Information and Disclosures

Updated: Jul 9, 2008

Differential Diagnoses

5-Alpha-Reductase Deficiency
Hypopituitarism
Adrenal Hypoplasia
Hypopituitarism (Panhypopituitarism)
Ambiguous Genitalia and Intersexuality
Kallmann Syndrome and Idiopathic Hypogonadotropic Hypogonadism
Androgen Insensitivity Syndrome
Klinefelter Syndrome
CHARGE Syndrome
Noonan Syndrome
Genital Anomalies
Panhypopituitarism
Growth Hormone Deficiency
Prader-Willi Syndrome
Hypogonadism
Smith-Lemli-Opitz Syndrome

Other Problems to Be Considered

X-linked adrenal hypoplasia congenita: Hypogonadotropic hypogonadism is associated with X-linked adrenal hypoplasia congenita and usually presents with lack of pubertal development. Primary adrenal failure occurs in infancy or early childhood. Mutations in the DAX1 gene are implicated.

Workup

Laboratory Studies

  • Chromosomal analysis is recommended to confirm chromosomal sex and to evaluate for associated genetic syndromes. If Prader-Willi syndrome is suspected, chromosomal analysis looking for a 15q11-13 band deletion of the paternally derived chromosome (70%), maternal uniparental disomy (25%), or methylation-specific paternal defect (5%) should be undertaken.
  • Gonadotropins (LH and FSH) reach pubertal levels in healthy male infants, peaking at age 1-3 months. Excessively high or low values during this time help to narrow the differential diagnoses.
  • 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).
  • Observe infants with micropenis (especially if other abnormalities associated with hypopituitarism are present) for evidence of 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 suspected hypopituitarism, growth hormone and cortisol levels can be measured after glucagon stimulation.
  • In infants with suspected hypopituitarism, measure total and free thyroxine (T4) levels to check for hypothyroidism. Thyrotropin-stimulating hormone (TSH) levels are low in secondary and tertiary hypothyroidism. Of interest, these children rarely have positive screen results for hypothyroidism in the newborn period.

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.

Other Tests

  • A GnRH-stimulation test can be performed to evaluate the pituitary gland's ability to respond and produce LH and FSH.
  • Testosterone therapy (testosterone enanthate or cypionate 25-50 mg every month for 3-6 mo) has diagnostic and therapeutic implications. No appreciable increase in penis size (<0.9 cm) with androgen therapy suggests androgen insensitivity.

More on Microphallus

Overview: Microphallus
Differential Diagnoses & Workup: Microphallus
Treatment & Medication: Microphallus
Follow-up: Microphallus
References
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References

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Further Reading

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Keywords

microphallus, micropenis, ambiguous genitalia, hypospadia, small genitalia, growth hormone deficiency, small penis, tiny penis, absent penis, 5-alpha reductase deficiency, partial androgen insensitivity syndrome, Prader-Willi syndrome, Klinefelter syndrome, Noonan syndrome, hypopituitarism, hypoadrenalism, electrolyte abnormalities, hypotension, shock, gender identity, cryptorchidism, gender reassignment, clitoromegaly, neonatal hypoglycemia, Kallman syndrome, adrenal insufficiency, cleft lip, cleft palate, midfacial hypoplasia, hypogonadotropic hypogonadism, congenital heart disease, renal agenesis, sensorineural deafness, visual abnormalities, synkinesia, septum pellucidum, optic nerve hypoplasia, septo-optic dysplasia, SOD, testicular degeneration, tall stature, gynecomastia, small firm testes, increased leg length, short stature, end-stage renal disease, hepatic fibrosis, hearing loss, Bardet-Biedl syndrome, CHARGE syndrome, Robinow syndrome, Rud syndrome

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Contributor Information and Disclosures

Author

Karen S Vogt, MD, Pediatric Endocrinologist, Department of Pediatrics, Division of Endocrinology, Walter Reed Army Medical Center
Karen S Vogt, MD is a member of the following medical societies: American Academy of Pediatrics, American Diabetes Association, Endocrine Society, and Lawson-Wilkins Pediatric Endocrine Society
Disclosure: Nothing to disclose.

Coauthor(s)

Merrily P M Poth, MD, Professor, Department of Pediatrics and Neuroscience, Uniformed Services University of the Health Sciences
Merrily P M Poth, MD is a member of the following medical societies: American Academy of Pediatrics, Endocrine Society, and Lawson-Wilkins Pediatric Endocrine Society
Disclosure: Nothing to disclose.

Andrew J Bauer, MD, Program Director, Department of Pediatrics, Division of Pediatric Endocrinology, Uniformed Services University of the Health Sciences
Andrew J Bauer, MD is a member of the following medical societies: American Academy of Pediatrics, American Thyroid Association, Endocrine Society, and Lawson-Wilkins Pediatric Endocrine Society
Disclosure: Nothing to disclose.

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, and Texas Medical Association
Disclosure: Nothing to disclose.

Medical Editor

Arlan L Rosenbloom, MD, Adjunct Distinguished Service Professor Emeritus of Pediatrics, University of Florida; 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, Florida Pediatric Society, Lawson-Wilkins Pediatric Endocrine Society, and Society for Pediatric Research
Disclosure: Nothing to disclose.

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine.com, Inc
Disclosure: Pfizer Inc Stock Investment from broker recommendation; Avanir Pharma Stock Investment from broker recommendation

Managing Editor

George P Chrousos, MD, FAAP, MACP, MACE, Professor and Chair, Department of Pediatrics, Athens University Medical School
George P Chrousos, MD, FAAP, MACP, MACE is a member of the following medical societies: American Academy of Pediatrics, American College of Endocrinology, American College of Physicians, American Pediatric Society, American Society for Clinical Investigation, Association of American Physicians, Endocrine Society, Lawson-Wilkins Pediatric Endocrine Society, and Society for Pediatric Research
Disclosure: Nothing to disclose.

CME Editor

Merrily P M Poth, MD, Professor, Department of Pediatrics and Neuroscience, Uniformed Services University of the Health Sciences
Merrily P M Poth, MD is a member of the following medical societies: American Academy of Pediatrics, Endocrine Society, and Lawson-Wilkins Pediatric Endocrine Society
Disclosure: Nothing to disclose.

Chief Editor

Stephen Kemp, MD, PhD, Professor, Department of Pediatrics, Section of Pediatric Endocrinology, University of Arkansas and 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, and Southern Society for Pediatric Research
Disclosure: Genentech, Inc. Honoraria Speaking and teaching; Pfiser, Inc. Honoraria Consulting

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