Pituitary Gland

The normal microscopic appearance of the pituitary gland

The adenohypophysis The neurohypophysis

The adenohypophysis contains three major cell types:

Cell types and function Somatotroph GH Mammotroph Prl Corticotroph ACTH Gonadotroph LH, FSH Thyrotroph TSH Null cells non-function

Hyperpituitarism - Adenoma Excess hormone production by the anterior lobe majority are Adenomas Hyperplasia and carcinoma are rare

Morphology of Adenoma Single and encapsulated Microadenoma is lesser than 1 cm Macroadenoma is larger than 1 cm, may reach up to 10 cm May show cystic changes and foci of necrosis Expand sella tursica  pressure effects (optic chaisma ) Pituitary apoplexy = haemorrage in the adenoma

Histology Sheets of uniform rounded cells with delicate scanty stroma Immunohistochimistry : Type of secertory hormone

Types of Pitutary adenoma

Growth hormone producing adenoma (5%) Usually large Evenly distributed into densely and sparsely granulated types E/M spherical cytoplasmic granules Immuno positive GH - Gh 1/3 and PRL Acidophilic cells

Growth hormone producing adenoma (5%) Gigantism (children) Acromegaly (adults) glucose intolrence, DM,osteoprosis, hypertension

Prolactin producing adenoma (20-30%) The most common functioning adenoma Majority are microadenamas and sparsely granulated E/M : small secretory granules Immuon:+sv PRL Women ---- microadenomas (amenorrhoea, glactorrhea syndrom ) Men and old females macroadenoam(late discovery)-----mass effect

Non secretory (Null cell ) adenoma (20%) Commenest cause of hypopituitarism Large ( macroadenoma) with atrophy of the surrounding pituitary tissue Immuno Variable 1/3 negative Chromphobic cells

Other rare types of adenomas ACTH producing adenoma FSH and LH – producing adenoma TSH-Producing adenoma Mixed

ACTH producing adenoma Usually microadenomas Give rise to Cushing’s disease E/M: +ve ACTH Basophilic cells Nelson’syndrome(bilatral adrenalectomy--- -secondry ACTH- producing pituitary adenoma

FSH and LH – producing adenoma Usually large No clinical features due to FSH and LH \ Mass effect High serum FSH and Lh E/M : secretary granules( 250 nm) Immuno : +ve FSH and LH Basophile cells

TSH-Producing adenoma Rare Produce TSH

Carcinoma of the pituitary Rare and non functioning Differentaited from adenoma by metastasis

Hypopituitarism Causes: Non_secrertory adenoma Pituitary necrosis (sheehan’s syndrom) The empty sella syndrome Pituiraty destruction (infection, radiation,surgical ablation,metastasis,vasculitis )

Clinical features : Deficiency of Gh : Dwarfism (children) Deficiency of Gonadotrophins : stereility Deficiency of ACTH or TSH : Hypofunction of the relevant endocrine glande

Posterior pituitary syndromes Rare Due to hypothalamic tumors (gliaoma,gangliocytoma,craniopharyngioma, GCT) Deficiency of antidiuretic hormone (ADH Deficiency)----- diabetes insipidus pyolyuria=polydipsia