Endo 1.07 The pituitary gland
• Anatomy and histology of the pituitary gland
• Growth hormone and its control
• Actions of growth hormone
• Excess and deficiency of GH
• Causes of pituitary failure
• Micro- and macroadenomas
• Prolactin and prolactinomas
• Arginine vasopressin and its control
• Actions of AVP
• Diabetes insipidus
Embryology of the pituitary gland
Pituitary in pocket of sphenoid bone
Reflection of dura mater allows the entire gland to be surrounded by dura
Thus the arachnoid membrane and CSF cannot enter the sella turcica
Anterior pituitary cells and their hormones
Chromophobes
Cell type
Chromophils
Acidophils Basophils
Growth hormone TSH, ACTH Prolactin LH & FSH
Histology of the pituitary gland
ACTH secreting cells
PRL secreting cells
Immunohistochemical identification of cells
secreting specific adenohypophyseal
hormones
HORMONE SECRETIONS OF THE ANTERIOR PITUITARY GLAND
Hormone % Pituitary cell population
TSH * 3-5%
ACTH * 15-20%
LH/FSH * 10-15%
GH # 40-50%
Prolactin # 10-15%
* Basophil # Acidophil
Growth hormone and prolacin
Actions of growth hormone
MAJOR FACTORS CONTROLLING MAJOR FACTORS CONTROLLING GROWTH HORMONE SECRETIONGROWTH HORMONE SECRETION
STIMULATION INHIBITIONGHRH Somatostatin
Hypoglycaemia Hyperglycaemia
Decreased fatty acids Increased fatty acids
Starvation IGF’s
Exercise/sleep Growth hormone
Stress
Androgens, estrogens Progesterone
-adrenergic agonists -adrenergic
Serotonin Serotonin antagonists
Dopamine agonists Dopamine antagonists
Symptoms of GH deficiencySymptoms of GH deficiency
•Decreased energy levels
•Social isolation
•Lack of positive well being
•Depressed mood
•Increased anxiety
Clinical features of GH Clinical features of GH deficiencydeficiency
• Increased body fat
• Decreased muscle mass
• Decreased bone density
• Increased LDL and decreased HDL cholesterol
• Decreased insulin sensitivity
• Decreased total fluid volume
Insulin induced hypoglycaemia to test for GH deficiency
Treatment of poor growth
• Growth hormone
• Growth hormone releasing hormone
• IGF (growth hormone insensitivity)
• Oxandrolone
Acromegaly
Clinical features of acromegaly
Symptoms
• Carpal tunnel syndrome
• Arthralgia/arthritis
• Excessive sweating
• Angina
• Diurnal drowsiness
• Polydipsia, polyuria
• Renal colic
• Menstrual irregularities
• Impotence
Signs
• Enlarged hands and feet, jaw protusion
• Osteoarthritis
• Greasy skin
• Hypertension
• Cardiomyopathy
• Obstructive sleep apnoea
• Retinopathy, neuropathy
• Renal stones
• Hypogonadism
Oral glucose load to test for GH excess
Causes of pituitary failureDevelopmental abnormalities
Trauma
• Inflammation - viral bacterial or fungal infections
• Infiltrative disease e.g. sarcoidosis
• Tumours of the brain or hypothalamus
• Radiation
• Tumours of the pituitary gland
Pituitary adenomas
Classified by size and hormones they produce
Microadenomas < 1cm diameter
Macroadenomas > 1 cm
30% prolactinomas
15% GH hypersecretion
10% ACTH secreting
10% gonadotrophinomas
< 1% TSH secreting
30% null cell (no hormone)
Chromophobic adenoma
Macroadenomas• Sellar enlargement
• suprasellar damage
• visual loss
• hypopituitarism
• extension into cavernous sinuses
Microadenomas• Tend to present with symptoms of hormonal excess
Treatment of pituitary adenomasTreatment of pituitary adenomas
• Medical
Dopamine agonists e.g. carbergoline/bromocryptine
GH analogue e.g. octreotide
GH receptor antagonists e.g. pegvisomant
• Surgical - transphenoidal surgery • Radiotherapy
Saggital MR scans of a) normal and b) a patient with a craniopharyngioma causing bitemporal hemianopia and
hypopituitarism
including
TRH
Control of prolactin secretion
Causes of Causes of hyperprolactinaemiahyperprolactinaemia
Common ~ 90%
• Dopamine D2 receptor antagonists (antiemetics/neurolepetics)
• Primary hypothyroidism (TRH)
Uncommon ~ 10%
• Pituitary tumour
• ‘Stalk syndrome’ (loss of dopamine)• Macroprolactinaemia (Immunoglobulin binds to
prolactin)
Coronal scans of a patient with a prolactinoma before and after
treatment with cabergoline
Synthesis of arginine
vasopressin and
oxytocin
Actions and control of vasopressin
Increase of vasopressin secretion in response to:
a) % increase in blood volume depletion
b) Increasing plasma osmolality
DIABETES INSIPIDUS
• CENTRAL - Impaired VP synthesis
• NEPHROGENIC - Resistance to VP
Lithium
CLINICAL TEST - 8h water deprivation/
saline load
SYMPTOMS - Polyuria/thirst
Tests for central and nephrogenic diabetes
insipidus
Changes in plasma osmolality (A) and urine osmolality (B) after 8 hours water deprivation and after an intramuscular injection of a long-acting synthetic vasopressin analogue, desmopressin
AVP response to an infusion of 3-5% sodium chloride
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