Turner syndrome and DSD — structured SAQ (15 marks)

(a) Diagnosis, mechanism and diagnostic test (3 marks)

One mark per point, maximum three. [1]

• Diagnosis: Turner syndrome (the phenotype of short stature, primary amenorrhoea and the stigmata of shield chest, cubitus valgus and webbed neck is classical).
• Mechanism of short stature: SHOX haploinsufficiency — the SHOX gene on the pseudoautosomal region of the X chromosome is essential for linear bone growth; loss of one copy drives the short stature and skeletal features.
• Diagnostic test: A full chromosomal karyotype with a minimum of 30 cells counted, with a Y-chromosome material screen (mosaicism and structural X variants are missed by 20-cell karyotypes or FISH alone).[1]

(b) Baseline non-gynaecological surveillance (4 marks)

One mark per investigation with justification. [1][2]

• Cardiac — echocardiogram AND cardiac MRI (echo alone misses the aortic arch and descending aorta; MRI is mandatory for the aorta which is the organ that kills via dissection).
• Renal ultrasound at diagnosis (horseshoe kidney and collecting-system anomalies are over-represented; shapes hypertension, infection and pregnancy risk).
• Thyroid function and antibodies, fasting glucose/HbA1c, lipids (autoimmune hypothyroidism and impaired glucose tolerance are common comorbidities).
• Audiology and bone age (progressive sensorineural hearing loss; baseline for the growth and GH plan).[1][2]

(c) Growth hormone and oestrogen timing (4 marks)

One mark per point, with the cardinal principle explicit. [1][4]

• Cardinal sequencing principle: growth hormone first; oestrogen second. Premature oestrogen fuses the epiphyses and steals final adult height.
• GH: started in childhood (after diagnosis, commonly around age 4 to 6 once growth falls off the centiles) to improve final adult height.
• Oestrogen induction: begun around age 11 to 12 (earlier than spontaneous puberty, because the streak gonads produce nothing), at low dose, ramped gradually over 2 to 3 years to mimic a normal pubertal curve.
• Progestogen added once breakthrough bleeding occurs or after 1 to 2 years of unopposed oestrogen, for endometrial protection; combined HRT continues until the usual age of menopause to protect bone and cardiovascular health.[1][4]

(d) Cardiac surveillance and fertility pathway (4 marks)

One mark per point. [1][3][4]

• Cardiac surveillance: baseline echocardiogram and cardiac MRI at diagnosis with interval imaging of the aorta; lifelong blood-pressure surveillance; clearance is non-negotiable before any pregnancy.
• Pre-pregnancy clearance: if the ascending aorta is dilated (per Gravholt 2024 thresholds), pregnancy is contraindicated.
• Fertility options: autologous oocyte retrieval is rarely possible (POI by presentation); oocyte or embryo donation is the commonest route; fertility preservation is occasionally an option in mosaic forms with residual follicles.
• Pregnancy in TS is high-risk: aortic dissection risk, hypertension, thyroid disease; mandates cardiac clearance and high-risk obstetric co-care.[1][3]