Pituitary disease

Pituitary lesions are present in >10% of the population.
Approximately 1 in 1000 people has a symptomatic pituitary tumour, which may cause clinical problems from mass effect, hormonal hypersecretion and impairment of normal pituitary function.
most frequent
- Pituitary adenomas
- Rathke’s cleft cysts
- Prolactinomas
normal anterior pituitary secretes 6 main hormones from five separate cell lineages:
- Adrenocorticotrophic hormone (ACTH) from corticotroph cells
- Thyroid stimulating hormone (TSH) from thyrotroph cells
- Growth hormone (GH) from somatotroph cells
- Prolactin from lactotroph cells
- Follicle stimulating hormone (FSH) and Luteinising hormone (LH) from gonadotroph cells.
The posterior pituitary releases two hormones
- Arginine vasopressin (also known as antidiuretic hormone)
- Oxytocin

– are the most common pituitary tumours – may be functional or non-functioning – defined as : microadenomas if <10 mm in maximum diameter macroadenomas if ≥10 mm in maximum diameter ‘giant’ pituitary adenomas if >4 cm in maximum diameter
Clinically non-functioning pituitary tumours (absence of any clinically significant hormonal hypersecretion, clinical problems due to mass effect (eg headaches, visual field defects) and hypopituitarism)	Silent gonadotroph adenoma Other non-secretory adenomas from corticotroph, lactotroph and somatotroph cell lineage Null cell adenoma
Functioning pituitary tumours	Prolactinoma GH-secreting adenoma (acromegaly) ACTH-secreting adenoma (Cushing’s disease) Rare functioning tumours – thyrotropinoma, FSH-secreting pituitary adenoma

may be due to a range of other conditions such as stress, pregnancy, lactation, nipple stimulation and medications (particularly anti-emetics and antipsychotics).
Up to 20% of cases may be due to ‘macroprolactin’, a biologically inactive immune complex between prolactin and immunoglobulin G.
Prolactinoma can be
- Microprolactinoma
  - Women have a higher prevalence
  - results in menstrual disturbance or galactorrhoea (alone or in combination).
- Macroadenomas
  - men are more likely to have it
  - have visual field defects and hypopituitarism at presentation

Overproduction of growth hormone causes excessive growth
In children, the condition is called gigantism
In adults, it is called acromegaly.
insulin-like growth factor-1 (IGF1)
- Circulating IGF1 arises predominantly from the liver and reflects integrated GH secretion.
- In contrast, measuring a random GH alone is not helpful as, because of its pulsatile nature, ‘high’ levels may indicate a secretory pulse in an unaffected individual.
- A significantly elevated IGF1 (>1.1 times the upper limit of the age-matched reference range) should then be a trigger for referral to an endocrinologist for further investigation and management.

Pituitary function test panel