Which initial investigations should be performed to confirm a diagnosis of hypopituitarism?

Initial investigations to confirm a diagnosis of hypopituitarism include:

• Assessment of pituitary hormone deficiencies by measuring basal hormone levels such as cortisol, thyroid-stimulating hormone (TSH), free thyroxine (FT4), gonadotrophins (LH and FSH), sex steroids (testosterone or oestradiol), growth hormone (GH) or insulin-like growth factor 1 (IGF-1), and prolactin.
• Morning serum cortisol measurement (8 am to 9 am) is important to assess for adrenocorticotropic hormone (ACTH) deficiency and adrenal insufficiency.
• Thyroid function tests (TSH and free T4) should be performed to evaluate for secondary hypothyroidism due to TSH deficiency.
• Gonadotrophin and sex steroid levels help identify hypogonadism related to pituitary dysfunction.
• Growth hormone deficiency can be initially screened by IGF-1 levels, but dynamic testing may be required for confirmation.
• Additional tests may include water deprivation test if vasopressin deficiency (diabetes insipidus) is suspected.
• Imaging of the pituitary with MRI is usually performed after biochemical confirmation to identify structural causes.

These investigations are particularly considered in people with symptoms consistent with hypopituitarism, such as fatigue, weakness, weight loss, hypotension, delayed puberty, sexual dysfunction, or after head injury with persistent symptoms.

Referral to endocrinology is recommended for further assessment and management once initial biochemical abnormalities are detected.

References: NICE NG232, NICE NG243, NICE NG145