Endocrine System

Actions of thyroid hormones

Increase basal metabolic rate Calorigenic action action that increases BMR Stimulates O2 consumption of almost all metabolically active tissues except adult brain, testes, uterus, lymph nodes, spleen & anterior pituitary T4 suppresses O2 consumption of the anterior pituitary because it inhibits TSH secretion Increase activity of Na/K ATPase in many tissues Increase Mitochondrial protein synthesis…

Biosynthesis of Thyroid hormone

 Recap: Thyroid follicular cells: Cells surrounding the follicle, there are microvilli projecting into the colloid from the apexes, with abundant endoplasmic reticulum. Inactive gland, colloid is abundant follicles are large cells lining the follicle are flat Active gland, follicles are small cells lining the follicle are cuboid/laminar Edge of cells are scalloped forming many small…

Antithyroid Drugs

Recap: Thyroid gland produces 2 iodinated hormones T3 (triiodothyronine) T4 (tetraiodothyronine) They promote metabolism, growth & development. Both hormone need iodine, the iodine binds to thyrosine in the thyroglobulin (colloid) to produce T3/T4. This process is called organification. Hyperthyroidsim: Graves disease Increase TSH receptor stimulation Increase production of T3 & T4 by thyroid gland Types…

Anatomy of the thyroid gland

Position of the thyroid gland: Infront of the neck In the midline Infront of the trachea Extends up to the thyroid cartilage Parts of the thyroid gland: 2 lobes Connected by an isthmus infront of the 2nd & 3rd tracheal ring Pyramidal lobe left end of isthmus Capsules: True capsule (thickening of the connecting tissue)…

Data interpretation of adrenal steroid disorders

Recap: Cushings  excess cortisol Congenital Adrenal Hyperplasia  decrease aldosterone & cortisol excess testosterone & DHEA-S Addison’s Disease  failure to produce all adrenal cortex hormone Conn’s syndrome/ Aldosteronism  Excess aldosterone Pheochromocytoma Excess epinephrine & norepinephrine. _____________________________________________________________________ General concept for investigation: 1) Establish whether it’s hyper/hyposecretion Use screening tests : Short synacthen (synthetic analogue of ACTH) dexamethasone suppression…

Quiz: Pituitary Gland

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PBL: Gigantism

Keywords: 12 year old student growing too tall too quickly (193cm) height increase last 2 years: 45cm gaining weight too excessively (over 150kg) occasional frontal headache (mass effect) need to pass urine frequently (too much AVP) visual acuity reduced High fasting blood sugar level High serum IGF-1 level High serum GH level High prolactin (stalk…

Tumours of the adrenal gland – Adrenal medulla

Pheochromocytoma Also known as: paraganglioma, chromaffinoma Intra-adrenal sympathetic paraganglioma Sporadic lesions: tend to be unilateral Familial lesions: tend to be bilateral 1.4-18% are incidentalomas Co-exist with extra-adrenal paragangliomas (can also occur outside adrenal medulla) Rule of 10 Pheochromocytoma associated genetic syndromes: Multiple Endocrine Neoplasia (MEN) type 2 Von-Hippel-Lindau (VHL) syndrome Neurofibromatosis (NF) type 1 Hereditary…

Tumours of the Adrenal Gland –Adrenal Cortex

OSPE: Refer histoloy of adrenal gland to identify the zones. TUMOURS OF THE ADRENAL CORTEX Adenoma Adenocarcinoma Adenoma Adenocarcinoma (malignant) Rare Hormonal symptoms (depending on the hormone hypersecretion) Virilization Hyperaldosteronism, Cushing’s Association with Li-Fraumeni syndrome (rare autosomal dominant hereditary disorder) Carney complex (autosomal dominant) CT scan. White: bone MRI. Bone is not white. _____________________________________________________________ Adrenal…

Adrenal Disorders – Congenital Adrenal Hyperplasia

It is an autosomal recessive syndrome: Insufficient cortisol syntesis Increased ACTH production –> increases cortisol to maintain circulating levels Stress cortisol – inadequate Mineralocorticoid synthesis affected 21 beta-hydroxylase deficiency & 17 alpha-hydroxylase deficiency for steroid hormone production 21 beta-hydroxylase deficiency: (refer diagram) Coding gene at chromosome 8 Mineralocorticoid defect results in hyperkalemia, hyponatremia & low…