S8) Pituitary Disorders

Question 1

Disorders of the pituitary gland are relatively rare.

What is the most common disorder?

Answer 1

The most common cause of pituitary malfunction is a benign tumour (adenoma)

Question 2

Most pituitary tumours are “non-functioning”.

What does this mean?

Answer 2

Non-functioning pituitary tumours contain tumour cells which themselves do not produce any hormone

Question 3

What is the usual consequence of non-functioning pituitary tumours?

Answer 3

These tumours can result in inadequate production of 1/more pituitary hormones due to physical pressure from the growing tumour on glandular tissue

Question 4

What are the clinical symptoms of non-functioning pituitary tumours?

Answer 4

Pressure on surrounding structures in the vicinity of the tumour result in:

• Headaches
• Visual problems (optic nerve)
• Vomiting
• Nausea

Question 5

Functional pituitary tumours are quite rare.

What does this mean?

Answer 5

Hypersecreting (functional) pituitary tumours contain tumour cells involved in the overproduction of 1/more of the pituitary hormones

Question 6

What are the clinical symptoms of functional tumours?

Answer 6

The clinical symptoms of hypersecreting tumours usually correspond to the systemic effects of the over secreted hormone

Question 7

Outline the clinical approach in the investigation of a suspected pituitary tumour

Answer 7

• Delineation of the anatomy, size and topographical location of pituitary / parapituitary mass (MRI scan)
• Assessment of visual field defects
• Assessment of endocrine function to determine hormonal excess/deficiency

Question 8

How might one assess the endocrine function in a patient with a suspected pituitary tumour?

Answer 8

• Measure hormone levels in blood
• Staining sections from a biopsy of the tumour with antibodies for the relevant hormone

Question 9

What is hypopituitarism?

Answer 9

Hypopituitarism is a state of insufficient pituitary hormone production, commonly due to a pituitary adenoma and rarely due to radiation therapy, inflammatory disease or head injury

Question 10

In light of hypopituitarism, what is the consequence of the adenoma?

Answer 10

Progressive loss of anterior pituitary function (GH and LH/FSH first)

Question 11

What is panhypopituitarism?

Answer 11

Panhypopituitarism is the deficiency of all anterior pituitary hormones

Question 12

Why aren’t ADH and oxytocin secretion usually impaired in hypopituitarism?

Answer 12

Secretion of ADH and oxytocin from the posterior pituitary is usually only significantly affected if the tumour affects hypothalamic function

Question 13

What are some causes of GH deficiency?

Answer 13

• Mass defects from pituitary adenoma
• Specific gene mutations e.g. GH-releasing hormone receptor
• Autoimmune inflammation

Question 14

What are the symptoms of GH hormone deficiency secondary to mass defects from a pituitary adenoma?

Answer 14

• Decreased tolerance to exercise
• Decreased muscle strength
• Increased body fat
• Reduced sense of “well-being”

Question 15

Why is GH deficiency often difficult to diagnose?

Answer 15

GH secretion is pulsatile, deficiency is often difficult to diagnose and a combination of direct and indirect measurements are required

Question 16

What are the symptoms of Gonadotropin deficiency in men and women secondary to mass defects from a pituitary adenoma?

Answer 16

• Women – infertility, oligomenorrhea, amenorrhea, lack of libido
• Men – impotence, lack of libido

Question 17

What are some causes of ADH deficiency?

Answer 17

• Hypothalamic tumour
• Extension of pituitary tumour
• Cranial radiotherapy
• Pituitary surgery
• Autoimmune infiltration
• Infections e.g. meningitis

Question 18

What is the main consequence of ADH deficiency?

Answer 18

Diabetes insipidus – excess excretion of dilute urine resulting in dehydration and an increased sensation of thirst (polydipsia)

Question 19

What is hyperpituitarism?

Answer 19

Hyperpituitarism is a state of excess pituitary hormone production mainly due to a functional hypersecreting pituitary adenoma

Question 20

There are three main conditions caused by excess pituitary hormone production from a hypersecreting pituitary adenoma.

Identify them

Answer 20

• Prolactin excess
• Growth hormone access
• ACTH excess

Question 21

Hyperprolactinaemia is the most common form of pituitary disorder and can cause a range of symptoms.

Identify five of these

Answer 21

• Galactorrhea (unexplained milk production – rare in men)
• Gynecomastia (hard breast tissue)
• Hypogonadism (diminished activity of testes or ovaries)
• Amenorrhea (cessation of menstrual cycle)
• Erectile dysfunction

Question 22

What is the most common cause of hyperprolactinaemia?

Answer 22

Prolactinoma – a pituitary adenoma that secretes prolactin

Question 23

Identify some physiological causes of hyperprolactinaemia

Answer 23

• Pregnancy
• Suckling
• Stress
• Exercise
• Drugs (antipsychotics & antidepressants)

Question 24

In four steps, explain how hypogonadism arises as a co-morbidity in hyperprolactinaemia

Answer 24

⇒ Increased plasma prolactin

⇒ Higher level of dopamine for negative feddback

⇒ Dopamine inhibits GnRH secretion from hypothalamus

⇒ FSH and LH secretion from the anterior pituitary inhibited

Question 25

How is hyperprolactinaemia usually treated?

Answer 25

• Dopamine receptor agonists e.g. cabergoline
• Trans-sphenoidal surgery (rare)
• Radiotherapy (rare)

Question 26

Growth hormone secreting pituitary adenomas are typically large (>10 mm in diameter).

In light of this, identify some of its associated symptoms

Answer 26

• Local mass effects – headache, visual field defects and other cranial nerve palsies
• Systemic effects – increased GH secretion & local IGF-1 production leads to gradual change in physical appearance

Question 27

Describe some the the changes in physical characteristics observed in growth hormone excess

Answer 27

• Coarse facial features: broad nose, thick lips, prominent supraorbital ridge
• Enlargement of the hands and feet
• Greasy skin
• Excessive sweating
• Deepening of the voice (hypertrophy of vocal cords)

Question 28

Explain why excess GH secretion can be associated with diabetes mellitus

Answer 28

GH antagonises the actions of insulin, so diabetes mellitus develops as a metabolic complication

Question 29

Three types of treatment options are available for patients with acromegaly.

Identify them

Answer 29

• Surgery
• Radiation therapy
• Drug therapy e.g. dopamine receptor agonists, synthetic somatostatin analogs

Question 30

What is a consequence of excessive ACTH secretion due to a pituitary adenoma?

Answer 30

Excess endogenous secretion of ACTH from the anterior pituitary gland is one of the causes of Cushing’s syndrome