From the Guidelines
Laboratory tests for micropenis diagnosis should include hormonal evaluations, such as testosterone, luteinizing hormone (LH), follicle-stimulating hormone (FSH), and growth hormone levels, as well as karyotype analysis to check for chromosomal abnormalities like Klinefelter syndrome, according to the most recent guidelines 1. When evaluating a patient with micropenis, it is essential to consider the underlying causes, which can be hormonal, genetic, or other disorders.
- Hormonal evaluations: These tests measure testosterone, LH, FSH, and sometimes growth hormone levels to identify any hormonal imbalances that may be contributing to the micropenis.
- Karyotype analysis: This test checks for chromosomal abnormalities like Klinefelter syndrome, which can be a cause of micropenis.
- Thyroid function tests (TSH, T3, T4): Hypothyroidism can affect penile development, so these tests are important to rule out any thyroid disorders.
- Additional tests: MRI of the pituitary gland to rule out tumors, and genetic testing for specific conditions associated with micropenis may also be necessary. These tests help determine the underlying cause of the micropenis, which guides appropriate treatment.
- Early diagnosis is crucial, as some hormonal treatments are most effective when administered during infancy or early childhood. The standard diagnostic criterion for micropenis is a stretched penile length more than 2.5 standard deviations below the mean for age, which should be established before ordering these laboratory tests 1.
From the Research
Micropenis Diagnosis and Treatment
- Micropenis is a medical diagnosis based on correct measurement of length, with a stretched penile length below the value corresponding to -2.5 standard deviation of the mean in a patient with normal internal and external male genitalia 2.
- The diagnosis of micropenis should be established, and the cause should be differentiated from other associated syndromes 3.
- Endocrinologic tests are important for the etiological evaluation of micropenis 2.
Lab Tests for Micropenis
- Plasma testosterone response to human chorionic gonadotropin testing can help determine the cause of micropenis 4.
- Androgen receptor (AR), 5α-reductase (5αR), and steroidogenic factor 1 (SF1) genes can be sequenced to detect molecular defects in the androgen pathway 4.
- Anti-Mullerian hormone and inhibin B levels should be evaluated in patients with isolated micropenis, even when plasma testosterone is in the normal range 4.
Treatment Approaches for Micropenis
- Testosterone therapy can augment penile size into the normal range for age in boys with micropenis secondary to fetal testosterone deficiency 5.
- Replacement therapy at the age of puberty can result in an adult-sized penis within 2 SD of the mean 5.
- Corrective surgery, such as total phalloplasty, can be performed in patients with realistic expectations, while more-conservative surgical techniques can improve length or girth with minimal enhancement 6.