5th June 2025

Hypopituitarism

Hypopituitarism is the partial or complete failure of the pituitary gland leading to insufficient hormones being produced. It can be caused by pituitary tumours and cyst, non pituitary tumours compressing pituitary, traumatic brain injury, pituitary surgery, radiation therapy to the sella, postpartum haemorrhage (Sheehan syndrome), subarachnoid haemorrhage and hypophysitis.

Presentation

Clinical presentation varies depending on which specific hormone is deficient. The hypopigmented skin lesions are due to ACTH and a-MSH deficiency. This presents as diffuse pallor in the genital area, breast, and face. ACTH deficiency can also lead to adrenal insufficiency and Addison’s disease.  ACTH deficiency can present acutely as weakness, dizziness, nausea, vomiting, circulatory collapse, fever, and shock. It can present chronically as fatigue, pallor, anorexia, and weight loss. In children they may fail to thrive and have delayed puberty. Other symptoms include hypoglycaemia, hypotension, anaemia, lymphocytosis, eosinophilia, and hyponatremia. Signs and symptoms can also be present from thyroid stimulating hormone deficiency, gonadotrophin deficiency, growth hormone deficiency, and antidiuretic hormone deficiency.

Investigation

Investigations include the endocrine assessment which is the measurement of basal anterior pituitary hormones are their respective target gland hormone levels. These will include ACTH, cortisol, thyroid stimulating hormone, free thyroxine, free triiodothyronine, follicle stimulating hormone, luteinising hormone, oestradiol, testosterone, and prolactin. Insulin-like growth factor 1 is measured for growth hormone secretion as direct growth hormone secretion is pulsatile. 

Serum electrolytes and serum and urine osmolality as ACTH and thyroid stimulating hormone deficiencies can cause hyponatremia. Hypernatremia is seen in diabetes insipidus. 

Water deprivation test is recommended in patients with symptoms of diabetes insipidus. 

MRI imaging of pituitary fossa or CT pituitary scan can be used to identify pathologies in the brain causing the hypopituitarism.

Treatment 

• The mainstay of treatment is replacement of the hormone deficiencies and treatment of the underlying cause or complication of hypopituitarism
• Surgical removal if a tumour is causing hypopituitarism 
• Glucocorticoid hormone replacement therapy for ACTH deficiency.
• For thyroid hormone deficiency, levothyroxine is given after glucocorticoid hormone replacement therapy if there is also ACTH deficiency. 
• Gonadal hormone replacement therapy (oestrogen and progestin) for premenopausal women with central hypogonadism. 
• Testosterone for men with central hypogonadism 
• Growth hormone replacement for growth hormone deficiency 
• Desmopressin for antidiuretic hormone deficiency