Steroid Analysis in Paediatrics with DSD Flashcards
What is early foetal sex determinaton/differentiation?
Determination: Y chromosome directs testes formation from indifferent gonad
Differentiation: Default is female unless influenced by hormones of testes (testosterone/AMH)
How is sex differentiaiton hormonally regulated?
Testosterone (Leydig cells) – external genitalia
- Testosterone and dihydrotestosterone are necessary for the formation of male external genitalia and the descending of the testes.
Anti-Mullerian hormone (Sertoli cells) – genital ducts
What are examples of Sex chromosome DSD?
- 45,X: Turner syndrome (& variants)
- 47,XXY: Klinefelter syndrome (& variants)
- 45,X/46,XY: Mixed gonadal dysgenesis and ovotesticular DSD
- 46,XX/46,XY: Chimeric and ovotesticular DSD
What are examples 46,XX DSD?
- Disorders of gonadal development: ovotesticular DSD, testicular DSD and gonadal dysgenesis
- Disorders of androgen excess: foetal, foeto-placental, maternal
- Other disorders: anatomical and syndromic
What are examples of 46,XY DSD?
- Disorders of gonadal development: complete/partial gonadal dysgenesis, gonadal regression and ovotesticular DSD
- Defect of androgen biosynthesis or action: androgen biosynthesis defects, androgen receptor defects, luteinising hormone receptor defects, AMH hormone/receptor defect
What are steroid metabolic pathways?
- Adrenal glands: glucocorticoid and mineralocorticoid synthesis
- Gonads: sex steroids (minor: adrenals – pathologically only relevant in females)
What is the basic structure of steroid?
- All steroids have the same basic four ring structure, the cyclopentanoperhydrophenanthrene nucleus.
- This forms a flat plane with functional groups siting above or below the plane of the ring.
- 100’s of possible structures makes steroid analysis challenging
What are advantages of using immunoassay for steroid measurement?
- Often cheap
- High throughput
- No great deal of operator skill required
- Often sensitive
What are disadvantages of using immunoassay for steroid measurement?
- Interference from closely related steroids: Neonates, Specific steroid disorders
- Interference of 11-deoxycortisol in the Siemens Centaur cortisol immunoassay in cases of 11β-hydroxylase deficiency CAH.
- High concentrations of 3β-hydroxy-5-ene steroids* (mostly sulphate conjugated) from foetal zone in first 2-3 months of life can cause interference in immunoassays
- First 2-3 days of life, foetal cortisol may be of maternal origin (in process of being cleared)
Why is Urine steroid profiling in the first 2-3 months challenging?
- High concentrations of 3β-hydroxyl-5-ene steroids (steroid sulphates) & low concentrations of cortisol/cortisone metabolites possessing multiple extra hydroxylations (e.g. at carbons 1- and 6-)
- Creates a complex pattern in initial 2-3 months of life
- Necessitates conjugate separation on sephadex columns prior to normal urine steroid profiling sample prep method
What are features of GC-MS compred to LC-MS/MS?
What are 46,XX DSD disorders of androgen excess?
Foetal Congenital adrenal hyperplasia (CAH) due to:
- 21-hydroxylase (CYP21A2) deficiency – 95% CAH cases, incidence 1 in 10,000
- 11β-hydroxylase (CYP11B1) deficiency (4-5% CAH cases)
- 3β-hydroxylase (HSD3B2) deficiency (very rare)
Foeto-placental
- Aromatase (CYP19A1) deficiency (rare)
Maternal
- Luteoma of pregnancy (very rare)
What is the clinical presentation of a female with ambiguous genitalia at birth?
- Clitoromegaly
- Fused labia
- Skin pigmentation?
- Salt-wasting (5-7 days after birth)
- Hypoglycaemia?
- Inguinal hernia (testes in groin)
What are the investigations for a female with Ambiguous Genitalia at Birth?
Karyotype: confirm XX
Abdominal ultrasound to confirm presence of uterus (exclude undescended testes)
Maternal history: exclude virilisation
Blood:
- 17-hydroxyprogesterone (basal / post-synatchen?)
- Electrolytes
- Cortisol /ACTH
- Renin/aldosterone
Urine: Urine steroid profile
What are features of 21-hydroxylase deficiency?
Gene: CYP21A2
46,XX Genital Phenotype: Ambiguous Genitalia
46,XY Genital Phenotype: Normal
Specific biochemical tests:
- 17-OHP (basal or post-synatcten)
- Urine steroid profile
What are clinical signs of 11β-hydroxylase deficiency?
Hypertension (11-deoxycorticosterone)
- presentation can occur throughout life as per 21-hydroxylase deficiency
What are clinical signs of 21-hydroxylase deficiency?
Variable degree of adrenal failure dep on severity of defect, therefore presentation can be
Classical:
- salt-wasting (both sexes)
- virilisation in females
Non-classical:
- mineralocorticoid production sufficient so do not salt-waste
- presentation due to androgen excess (neonates: ambiguous genitalia; childhood: precocious puberty; adulthood: amenorrhoea/fertility issues
What are features of 11β-hydroxylase deficiency?
Gene: CYP21A2
46,XX Genital Phenotype: Ambiguous Genitalia
46,XY Genital Phenotype: Normal
Specific biochemical tests:
- 11-deoxycortisol (basal or post-synatcten)
- Urine steroid profile
What are features of 3β-hydroxysteroid deficiency?
Gene: HSD3B2
46,XX Genital Phenotype: Clitoromegaly
46,XY Genital Phenotype: Ambiguous
Specific biochemical tests: Urine steroid profile (but only reliable >2-3 months post-term birth)
What are signs of 3β-hydroxysteroid deficiency?
- Primary adrenal failure
What are feature of P450 Oxido-reductase defects?
Gene: POR
46,XX Genital Phenotype: Ambiguous
46,XY Genital Phenotype: Ambiguous
Specific biochemical tests: Urine steroid profile
What are signs of P450 Oxido-Reductase deficiency?
- Sometimes associated with Antley- Bixler syndrome
What do invesitgations show in 21 Hydroxylase Deficiency?
Blood:
- ↑ 17OHP (& 21-deoxycortisol & androgens, ↓ cortisol)
Urine:
- ↑17OHP metabs (esp. 17-hydroxypregnanolone, pregnanetriol and 11-oxopregnanetriol & androgen metabs; ↓ cortisol metabs)
What is required to test non-classical CAH due to CYP21A2?
In non-classical CAH synatchen testing may be required
