Pituitary gland

Gross anatomy of the pituitary gland

The average weight of the pituitary gland at birth is about 100 mg. Rapid growth occurs in childhood, followed by slower growth until the adult weight (approximately 500–600 mg) is attained in the latter part of the second decade. The adult hypophysis measures approximately 10 mm in length, 10 to 15 mm in width, and about 5 mm in height

Although the adult hypophysis typically measures less than 1 cm in its greatest dimension and weighs less than 1 g, its small size gives a wrong idea about its importance and complexity

Embryogenesis of the pituitary gland The pituitary gland originates from two

discrete parts of the developing embryo ,(neural & epithelial)

The ant. Lobe develop from the roof of the mouth(epith.)and called adenohypophysis

The post. Lobe develop from the brain(neural)called neurohypophysis

On average, the female gland is almost 20% heavier than the male gland primarily because of relative differences in the size of the pars distalis(adenohypophysis).

Furthermore, the weight of the gland increases by 12% to 100% during pregnancy because of enlargement of the pars distalis.

the size of the pars nervosa remains relatively constant.

The volume of the pituitary gland decreases with aging

The pituitary gland derives its blood supply from two groups of arteries. The superior hypophyseal artery (SHA) primarily supplies the anterior lobe, whereas the inferior hypophyseal artery (IHA) is primarily related to the pars nervosa. The SHA can arise from the supraclinoid portion of the internal carotid artery (ICA) or from the posterior communicating artery, whereas the IHA arises from the meningohypophyseal trunk, a branch of the cavernous segment of the ICA

The oculomotor nerve, trochlear nerve, and first two divisions of the trigeminal nerve are embedded in the lateral wall of the cavernous sinus, lying between the endothelial lining and the dura mater, whereas the abducens nerve is contained within the sinus itself

Pituitary tumors

Classifications:a. classification of pit.tumors and tumor like conditions

1.tumors derived from adenohypophyseal cells(adenoma, carcinoma)

2.other primary tumors of sella turcica.(angioma,craniopharyngioma,meningioma,optic nerve glioma

3.metastatic tumors4.tumor like conditions(abscess)

craniophryngioma

Arise from anterior superior margin of pituitary gland.

Lined by stratified squamouse epithelium

All CP had solid and cyctic part,contain cholestrol crystal (machine oil)

CP donot undergo malignant degeneration but malignant behaviour,difficult cure (C.P adherant to the major art. At the base of the brain(int. carotid)

craniophryngioma

Calcification in plain x ray 54% in childhood ,20%, in adult , 2.5 -4 % of all brain tumor 9% of children brain tu. ,peak incidence age 5-10 year 55-85% five years survival rate 5-10-% mortality due to hypothalamic

injurey High recurrence rate in 1st 1-3 years

Signs & symptoms

SymptomsHeadache,nausea &vomiting,visual

loss, short stature,mental problems,diplopiaSignsPapilledema ,visual defect,endocrine

dysfunction,cranial nerve palsy,psychatric abnormality

Management

DiagnosisPlain x-ray, C.T , M.R.I, endocrine

assessmentTreatmentSurgery(hydrocephalus,cyst drainage)Medical replacement(steroids,A.D.H

replacement with fluid)Radiotherapy(better results in children

than adults)

Treatment of hydrocephalus

Ommaya reservior

Radiotherapy

Linear accelerator

Gamma knife radiosurgery

Pituitary adenoma

b.classification of pituitary adenomas according to endocrine function

-SECRETORY1.prolactinoma

2.GH adenoma

3.ACTH adenoma

4.FSH/LH adenoma

5.T.S.H adenoma

6.plurihormonal adenoma(more than 1 hormone secretion

-ADENOMA WITH NO APPERANT HORMONAL FUNCTION

 

c. Classification according to size on radiographic appearanceGrade-0 intrapit. Adenoma ,diam.less than 1 cm,normal sella

Grade-1 intrapit.ad.,diam.less than 1 cm,focal bulging or minor changes in sellar shape

Grade-2 intrasellar adenoma,diam. More than 1 cm,enlarge sella, no erosion

Grade-3 diffuse ad.,diam more than 1 cm,enlarge sella, localized erosion

Grade-4 invasive ad.,diam more than1 cm,extensive destruction of bony struc.(gohst sella)

Adenoma Arise from adenohypophyseal cells 10-15% of intracranial tu. Benign tu. Mostly,slow-growing1.Adenoma with no apparent hor. Func.

(20%)2.Secretory

adenoma(prolactinoma,GH,TSH,ACTH,FSH/LH adenoma

PROLACTINOMA

Most common functional pituitary tu., accounting for approximately 25% of all pit. Tu.& 3% of all intracranial tumors

Prolactin level elevated(200-300ng/ml) ,lower levels may be found if there is other tumors compressing the stalk and interrupt the flow of inhibitory dopamine.

Clinical presentation

Mass effect (visual field defect(bitemporal hemianopia),impaired acuity,headache,rarely 3rd,4th,6th nerve palsies,hydrocephalus, other endocrinological symp.)

women symptoms(primary or secondary amenorrhoea and infertility, galactorrhoea)

Men symptoms(decreased libido,impotence,oligospermia)

Hyperprolactinoma suppresses the hypothalamic –pituitary-gonadal axis) leading to hypogonadism in both sexes

DIAGNOSIS

Endocrine testing1.fasting level of prolactine(>150ng/ml

indicate that the cause pit.adenoma, if it >1000ng/ml ,it signify the invasiveness of tu. that extend to cavernous sinus)

2. other hormonal assessment(pit.-thyroid ,pit.-gonadal(FSH-LH,testosterone),pit-adrenal(a.m cortisol),antidiuretic hor,(urine &serum electrolytes)

Neuroimaging studies

C.T SCAN of sella with thin slices(1.5-2 mm)plus contrast ,to exclude ac. Haemorrhage.

MRI of sellar & parasellar(<2.5mm slices)Cerebral angiography or MRI angio to

exclude aneurysms.

TREATMENTMode of treatment depend on :

1.size of tumor2.the level of serum prolactin.3.the patient age & overall health.4.The patient`s tolerance of or

compliance with medical therapy.5.the patient desires fertility.6.surgical risk factors

Indications of surgical treatment of prolactinoma

1.Non invasive tu. With prolactine level(150-500ng/ml) and patient not wish to take long term medications.

2.A woman with non invasive tu.,prl. (<500 ng/ml),who desires pregnancy.

3. A Woman with macroprolactinoma who desire pregnancy.

4.Macroprolactinoma with s.prolactin>500ng/ml

5.Pituitary apoplexy as a complication of prolactinoma>

6.A prolactinoma in pregnant patient causing mass effect( visual loss)

7.A prolactinom that is not respond to medical treatment

8.A recurrent prolactinoma

SURGICAL TREATMENT

Craniotomy (rt. Frontal)

Trans-sphenoidal & transnasal approach

craniotomy

transsphenoidal

COMPLICATIONS OF TRANS-SPHENOIDAL

1.C.S.F leak2.Meningitis3.Hypopituitarism & Diabetes insipidus4.pneumocephalus

RADIOTHERAPY:

1.conventional external radiation

Adverse effect(hypopituitarysm, optic nerve or chiasmal injury,brain radionecrosis,carcinogenesis)

2.stereotactic radiosurgery (GAMMA KNIFE RADIOSURGERY).

Indication(microadenoma or macroadenoma<5 cm)

Gamma knife

Pituitary apoplexyAcute haemmorrhagic necrosis of a

pituitary adenoma&adjacent pituitary tiss.

Predisposing factors:pregnency,endocrinologic manipulations(estrogen adminstration,bromocriptine medication),H.injury,chronic cough&sneezing,anticoagulant drugs,cerebral angio.,radiotherapy

Symptoms &signs

Headache,nausea & vomiting, diplopia&visual impairment, compression of cranial n.s in one or both cavernous sinuses,ophthalmoplegia, meningeal irritation,photophobia

Diagnosis(MRA,ANGIO,CT,CLINICAL)Treatment :surgery

Acromegaly

(1) to control clinical signs while preserving pituitary function with as minimal adverse effects as possible. (2) to normalize excessive growth hormone (GH) and IGF-1 secretion as quickly as possible, thereby achieving biochemical control(3) to avoid the expansion of the tumor volume and if possible reduce tumor size in order to relieve any symptom due to tumor mass.

TREATMENT ALGORITHM

Neurosurgery 56:877-885, 2005)SRL=Ssomatostatin receptor ligand ,DA=dopamine agonist)

Indications for surgery include active acromegaly visual loss and other forms of mass

effect pituitary tumor apoplexy failure of other therapies (medical,

radiation).

visual compromise develops quite slowly and gradually

surgical decompression of visual pathways is usually recommended unless the compression can be resolved by medical treatment.

Undisputedly, the most rapid and reliable relief from optic nerve and chiasmal compression is being achieved by surgery, which is particularly appreciated if severe loss of vision occurred acutely, as in pituitary apoplexy

Hormonal oversecretion for patients with secretory pituitary adenoma increasing the morbidity and mortality.

Clinical diagnosis of these diseases is generally considered an indication for surgery.

Because surgery is still generally considered the most rapidly acting and cheapest long-term solution for most patients.

recent data suggest that hypopituitarism can also be considered an indication for surgery since pituitary function may be improved following decompression of the gland by selective tumour resection

A conservative approach is usually recommended in incidentally detected lesions, which became more frequent with the widespread availability of MR imaging.

BUT the progression of a tumour, which is clearly documented in the MR, is another indication to surgically attack a lesion that has already shown an increase in size.

Re-operations should be strongly considered if a resectable lesion has not been excised

satisfactorily by the primary intervention patients with recurrent disease, if

adjunctive medical or radiation therapy failed to achieve control of the adenoma

in symptomatic progressions of residual tumours. It seems easier for an expert neurosurgeon with an excellent success and a low complication rate to recommend an operation for a pituitary tumour

Radiotherapy Conventional radiotherapy Stereotactic radiosurgery

Remission rate (50-60%) Time of remission delayed

by several years(10y). Propsed for patients with

aggressive adenoma when surgery cannot allow biochemical control.

Hypopituitarism increases with time (50-80%),also its more with previosly altered pit. Function(by surgery)

Remission rate(17-96%) faster growth hormone

hypersecretion decline.(2y)

requires a well defined target volume.

be used as an alternative primary treatment to surgery.

Hypopituitarism(0-33%)

Optic neuropathy, radionecrosis, vascular injury

were much lower in gamma knife than conventional radiothearapy

Pre.

Post

Post medical.