endocrine- pituitary Flashcards
List pure and mixed endocrine organs
Pure endocrine organs •Pituitary •Thyroid •Parathyroid •Adrenal – Cortex & Medulla
Endocrine components in mixed organs
•Pancreas
•Ovary
•Testis
Explain the regulatory control mechanisms of the endocrine system
Endocrine glands under regulation by stimulatory and inhibitory signals facilitated by
- trophic releasing hormones
- trophic hormones
- feed back inhibition
- release inhibiting hormone
Outline the diseases of the endocrine organ
Hyperfunction – excessive secretion of hormones
•Hypofunction – decreased secretion of hormones
•Enlargement / mass effect
•Functional
•Non functional
Explain causes of hypofunction and hyperfunction
HYPERFUNCTION •Hyperplasia or neoplasia of hormone secreting cells
•Secondary hyperfunction – increased stimulation / decreased feedback inhibition
•Ectopic hormone production
HYPOFUNCTION Primary hypofunction •Congenital absence •Hypoplasia •Destruction of the gland Secondary hypofunction •Absence of trophic hormones Pseudohypofunction •Target organ receptors not functioning
What is the weight and measurement of the pituitary gland?
500 mg , 10-15mm
What is the structure of the pituitary lobe?
Anterior lobe(adenohypophysis)- derived from Rathke’s pouch
Post lobe(neurohypophysis) - derived from 3rd ventricle
Where is the pituitary gland located?
Sella turcica between the hypothalmus and pineal gland
What are the 3 cell types of anterior pit?
acidophils, basophils, chromophobes
How is the anterior pit controlled?
By positive/negative stimulus from hypothalamus
Hypothalamus secretes the following hormones to stimulate release of trophic hormones from the anterior pit.
Corticotropin releasing hormone: adrenocorticotropin hormone
Thyrotropin releasing hormone: thyroid stimulating hormone
Growth hormone releasing: Growth hormone
Gonadotropin releasing hormone : FSH, LH
Somatostatin- inhibitory to growth hormone
Dopamine- inhibitory to prolactin
What are the causes of hyperpituitarism ?
functioning adenoma
rarely a carcinoma; must show mets for diagnosis
very rarely other pathology like hyperplasia
Describe pituitary adenomas
10% primary intracranial neoplasms
most common 40-60 yrs
rarely apart of MEN type 1
Two types
Functional (hormone secreting neoplasm)
Non functional adenoma (30%)
further classification
microadenoma <1cm
macroadenoma >1cm
What is the most common functional pituitary adenoma?
Prolactinoma - 30% Somatotrophic adenoma- 15% Adrenocorticotrophic adenoma- 10% Mixed- 5% Gonadotrophic adenoma-5% Thyrotropic - rare
What are the symtoms aw pituitary adenomas?
1.Hormone overproduction •Prolactin •GH •ACTH •TSH •FSH/LH 2.Space effect •Incidental on imaging •Optical chiasm pressure – bitemporal hemianopia •Hormone deficiency •Rarely symptoms of increased ICP
What is a prolactinoma and a/w symtoms
a/w excess release of prolactin
Besides pressure effects, in males - asymptomatic, libido ,infertility
females: amenorrhea, galatorrhea , sterility
What besides a prolatinoma causes increase in prolactin levels?
pregnancy/lactation
stalk compression
How do you diagnose a prolactinoma?
Assess pituitary function
by checking thyroid function - free T4, TSH (TSH dependent prolactin release can occur as TRH has a +ve effect on prolactin release)
gonadal axis function - testosterone, oestrogen, FSH, LH (prolactin can inhibit GRH)
IGF-1 - if low deficiency in GH
Insulin tolerance test- assess cortisol and GH response to hypoglycaemia
serum prolactin
short synacten test- IM synthetic ACTH which assesses cortisol at baseline and 30 mins
Do MRI
How are prolactinomas treated?
Surgery
dopamine agonist ; bromocriptine
What are features of growth hormone ademona/somatrotropic adenomas
If this occurs pre pubertal- gigantism
Post pubertal - acromegaly
can be bi hormonal (+ve prolactin)
What is the clinical presentation for acromegaly?
Appearance: prognathism brow protrusion enlarged hand and feet large tongue broad nose
Other:
joint pain , carpel tunnel syndrome, diabetes and deafness
What is the pathogenesis of acromegaly?
GH secreted from ant pituitary then stimulates liver to secrete insulin like growth factor which is the primary mediator for growth hormone effects.
Acromegaly occurs when there is an excessive, unregulated secretion of GH typically from pit adenoma(somatotropic adenoma).
Other causes- hypothalmic dysregulation and increased secretion of GHRH
What are the effects of acromegaly?
Tissue expansion
Headache
Visual defects
Cranial nerve palsies
Hormone hypersecretion
Morphological changes - changes in appearance as aforemention and as well as acral swelling, organomegaly, skin tags, colon polyps
Endocrine changes
Metabolic changes eg DM, insulin resistance hypertension , LV hypertrophy
cardiac death
Hypopituitarism
Lethargy, loss of libido, infertility
Treatment options for growth hormone adenoma?
Surgery Radiotherapy Meds: inhibit release of GH dopamine agonists:carbegoline somatostatin analogues: octreotide, lanreotide inhibit GH receptors: pegvisomant
Replacement of pit hormones
Treat co morbidities eg hypertension , DM etc.
What are some other adenomas?
ACTH producing
•Usually microadenomas
•Silent
•a.w Cushing’s disease (hypercortisolism due to xs ACTH from pituitary)
Gonadotrophic
•Hormonal effects can be subtle
•Can be large
Thyrotrophic
•Rare
Null-cell
•Usually only detected via mass effect when large
What are the common causes of hypopituitarism?
Adenoma- compression of normal tissue
Trauma
Latrogenic (surgery/radiation)
Ischaemic necrosis (sheehan’s syndrome)
