Hypopituitarism and pituitary lesions — structured clinical encounter

Station brief (candidate)

You have ten minutes to assess this boy, establish the likely diagnosis, outline the investigation and replacement plan, and address the family's questions. The examiner will prompt you at intervals. A suprasellar lesion causing hypopituitarism is the leading diagnosis, and the family is anxious about the word "tumour". [5]

Key clinical features to elicit

Establish the growth story with serial heights, the height velocity over at least six months, the mid-parental target range and a bone age, because a low velocity with downward crossing points away from constitutional delay. Ask about the headaches and any morning vomiting that suggest raised intracranial pressure, formally test the visual fields, and screen the other axes with questions about energy, cold intolerance, thirst, polyuria and pubertal signs. [1]

Diagnostic work-up

Screen the axes with paired hormones — IGF-1, free thyroxine with thyroid-stimulating hormone, an early-morning cortisol with adrenocorticotrophin, gonadotrophins with testosterone, and prolactin — and pair a serum with a urine osmolality if thirst or polyuria is present. Confirm growth hormone deficiency with a stimulation test because secretion is pulsatile, and confirm the cortisol axis with a low-dose Synacthen or insulin tolerance test if the morning cortisol is indeterminate. Then image the hypothalamus and pituitary with contrast-enhanced MRI. [7]

The lesion and its markers

The combination of growth failure, headache and a bitemporal field defect points to a suprasellar mass compressing the chiasm, most likely a craniopharyngioma — classically cystic and calcified. If instead the MRI shows a thickened stalk with central diabetes insipidus, send serum and cerebrospinal-fluid beta-human-chorionic-gonadotrophin and alpha-fetoprotein for a germinoma. Refer to neurosurgery and oncology for definitive treatment of the lesion. [5]

Replacement — the safe order

Replace hormones in the fixed safety order: hydrocortisone first, with sick-day and stress dosing and an emergency injectable, then levothyroxine once cortisol is covered, then growth hormone by daily subcutaneous injection titrated to height velocity and IGF-1, then sex steroids to induce puberty at the appropriate age. Treat any central diabetes insipidus with desmopressin titrated to thirst and osmolality, watching for hyponatraemia from over-treatment. Never start thyroxine before glucocorticoid. [10]

Family conversation

Explain to the family that this is a growth and hormone problem caused by a lesion near the pituitary gland, that the imaging and blood tests will define exactly which hormones are affected, and that most of the hormones can be safely replaced with tablets and injections. Be honest that a suprasellar tumour needs a neurosurgical and oncology team, that replacement is usually lifelong, and that vision and growth are carefully monitored. Reassure them that the danger of a cortisol crisis is managed with a clear emergency plan they will be taught. [11]