The endocrine system

1. The endocrine system DrMaramAbdaljaleel, MD School of Medicine, University of Jordan

2. Pituitary gland Posterior pituitary Anterior pituitary

3. Pituitary gland • Anterior pituitary. • Posterior pituitary. Diseases include: • Hyperpituitarism. • Hypopituitarism. • Local mass effect.

4. HYPERPITUITARISM • pituitary adenoma arising in the anterior lobe is the most common cause of hyperpituitarism • Other causes includes; pituitary hyperplasia and carcinomas, secretion of hormones by some extrapituitarytumors, and certain hypothalamic disorders

5. Pituitary adenoma • Pituitary adenomas are classified on the basis of hormone(s) produced by the neoplastic cells. • Pituitary adenomas can be macroadenomas (>1 cm) or microadenomas (<1 cm). • Pituitary adenomas can be: • functional (hormone producing) • nonfunctioning (not producing hormone) • Silent (hormone production at the tissue level only, without clinical manifestations).

6. adenomas usually are composed of a single cell type and produce at most a single predominant hormone, but some pituitary adenomas secrete two different hormones (GH and prolactin is the most common combination); rarely, plurihormonal.

7. Pathogenesis: • mutations in GNAS resulting in activation of the α subunit of a G-protein. • 5% of adenomas arise with familial syndromes.

8. Figure 15-6 Pituitary macroadenoma, gross

9. Figure 15-7 Pituitary adenoma, microscopic

10. 1. Prolactinomas • Are the most common type of functioning adenomaaccounting for 30% of all clinically recognized cases • Hyperprolactinemia causes amenorrhea, galactorrhea, loss of libido, and infertility. • Because amenorrhea is one of the symptoms of hyperprolactinemia,, prolactinomas in premenopausal women are diagnosed at an earlier stage • By contrast, the effects of hyperprolactinemia are subtle in men and older women tumor may reach a large size before coming to clinical attention.

11. 2. Growth Hormone-Producing Adenomas • The second most common type of functioning pituitary adenoma. • Results in excessive growth hormone production

12. 1. If a growth hormone-secreting adenoma occurs in prepubertalchildren(before the epiphyses close) it results in gigantism generalized increase in body size, with disproportionately long arms and legs. 2. If elevated levels of growth hormone present after closure of the epiphyses, individuals develop acromegaly a. Growth is most conspicuous in soft tissues, skin, and viscera. b. Jaw enlargement, protrusion and separation of the teeth. c. Enlarged hands and feet, with broad sausage-like fingers.

13. Persistent growth hormone excess is associated with metabolic abnormalitiesnamely diabetes mellitus. • because of growth hormone–induced peripheral insulin resistance, which “blunts” the body’s response to elevated glucose levels

14. 3. Adrenocorticotropic Hormone–Producing(Corticotroph Cell) Adenomas: • Causes hypercortisolism (Cushing syndrome) • When the hypercortisolism is caused by excessive production of ACTH by the pituitary, the process is designated Cushing disease.

15. The posterior pituitary Produces two hormones: oxytocin and ADH. ADH : 1. ADH deficiency causes diabetes insipidus, excessive urination (polyuria), polydipsia and increased serum sodium and osmolality. • Causes : head trauma, neoplasms, inflammatory conditions of hypothalamus and posterior pituitary, or idiopathic. 2.Syndrome of inappropriate ADH (SIADH) secretion, resorption of excessive amounts of free water, with resultant hyponatremia, cerebral edema and neurologic dysfunction.

16. Thyroid gland • Hyperthyroidism • Hypothyroidism.

17. Figure 15-11 Normal thyroid, microscopic The normal thyroid gland is composed of round follicles lined by cuboidal epithelial cells and filled with colloid, a storage product containing thyroglobulin that is metabolized to release thyroid hormones (T4 and T3) under the influence of TSH released from the anterior pituitary thyrotrophs, which sense levels of circulating thyroid hormone.