Investigations
1st investigations to order
chromosome analysis (karyotype)
Test
On initial evaluation, should be performed with at least 30 metaphases to assess for mosaicism. Results can usually be obtained within 72 hours.
A rapid result may be obtained using a fluorescence in situ hybridisation (FISH)/polymerase chain reaction (PCR) for sex-determining region Y (SRY).
Result
may be normal or show evidence of mosaicism
serum electrolytes and glucose
Test
May be deranged due to aldosterone deficiency and glucocorticoid deficiency.
Result
low sodium/high potassium in salt-wasting forms of congenital adrenal hyperplasia; typically not abnormal before day 4 of life
pelvic ultrasound
Test
Will determine presence of Müllerian structures (uterus). Ovaries and fallopian tubes often not visible on ultrasound.
May also help locate site and morphology of gonads.
Adrenal glands are usually relatively large in the neonatal period.
Result
presence or absence of uterus or undescended testes; this result may give an indication of Sertoli's cell function or responsiveness to anti-Müllerian hormone; adrenal glands may have a heterogeneous ‘cerebriform’ pattern in 21 hydroxylase deficiency
Investigations to consider
serum 17 hydroxyprogesterone
Test
Levels should always be obtained, especially in the absence of palpable testes, as the most likely diagnosis is congenital adrenal hyperplasia (CAH) secondary to 21 hydroxylase deficiency.
Is part of the newborn screen in some countries.
Test after 48 hours of age.
Result
markedly elevated in 21 hydroxylase CAH
plasma renin activity
Test
High activity in the setting of salt-wasting. Congenital adrenal hyperplasia (CAH) due to 21 hydroxylase deficiency and other causes of salt wasting cause elevated levels.
Test after 48 hours of age.
Result
elevated in salt-wasting CAH
serum 11 deoxycortisol and 11 deoxycorticosterone
Test
In 46,XX congenital adrenal hyperplasia (CAH) not due to 21 hydroxylase deficiency, measurement of additional adrenal precursors may lead to a diagnosis. 11 beta-hydroxylase deficiency is the second most common cause of CAH after 21 hydroxylase deficiency.
Test after 48 hours of age.
Result
elevated in CAH due to 11-beta-hydroxylase deficiency
serum testosterone
Test
Low testosterone level in a 46,XY baby with atypical genitalia should be followed up with a human chorionic gonadotrophin (hCG) stimulation test to further assess testicular function.
An elevated ratio of testosterone to dihydrotestosterone is characteristic of 5 alpha-reductase deficiency.
A reduced testosterone/androstenedione ratio is observed in 17 beta-hydroxysteroid dehydrogenase deficiency.
Test after 48 hours of age.
Result
low levels will be observed in testosterone biosynthetic and testicular function defects; elevated in 5 alpha-reductase deficiency or 21 hydroxylase deficiency, 11 beta-hydroxylase deficiency
serum dihydrotestosterone
Test
Elevated ratio of testosterone to dihydrotestosterone is characteristic of 5 alpha-reductase deficiency.
Test after 48 hours of age.
Result
low in 5 alpha-reductase deficiency
serum LH and follicle-stimulating hormone (FSH)
Test
Levels indicate activity of the hypothalamic-pituitary-gonadal axis, although low levels in the first week of life do not necessarily indicate hypogonadotrophic hypogonadism. Assessment at 2 to 4 months of life may be more revealing when LH and FSH levels increase physiologically.
Test after 48 hours of age.
Result
low or normal in hypogonadotrophic hypogonadism
adrenocorticotropic hormone (ACTH) stimulation test
Test
May reveal abnormalities of glucocorticoid synthesis.
Test after 48 hours of age.
Result
low cortisol levels observed in some forms of congenital adrenal hyperplasia and disorders of adrenal development
human chorionic gonadotrophin (hCG) stimulation test
Test
Helps assess the ability of the Leydig cells of the testes to respond to hCG and produce testosterone.
Test after 48 hours of age.
Result
low testosterone with testosterone biosynthetic and testicular function defects; high testosterone to dihydrotestosterone ratio in 5 alpha-reductase deficiency; low ratio of testosterone to androstenedione in 17 beta-hydroxysteroid-dehydrogenase deficiency
anti-Müllerian hormone (AMH)
Test
Previously called Müllerian-inhibiting substance. Can be a useful indicator of testicular Sertoli's cell function in a 46,XY DSD and in chromosomal DSD.
Test after 48 hours of age.
Result
AMH levels are age- and sex-dependent
urine steroid profile
Test
Helps assess disorders of adrenal steroidogenesis. If CAH is suspected and 17 hydroxyprogesterone levels are not markedly elevated, adrenal precursors should be further evaluated by profiling.
Spot sample should be taken before treatment with glucocorticoids.
Sample analysis takes at least several days and so treatment should not be delayed if CAH is suspected.
Test after age 48 hours.
Result
may help identify rarer causes of CAH, such as 11 beta-hydroxylase deficiency; will only tease out a defect in 5 alpha-reductase after age 2 to 3 months
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