WEEK 5 - Endocrine Disorders

Consists of groups of cells (glands) that make hormones and release them directly into the bloodstream (ductless)

• They are chemical messengers • They control the activity of the cells they bind to • Hormones will only bind to cells that have their receptors on their surface

Hypothalamus Pineal Pituitary Parathyroid Thyroid Thymus Adrenal (cortex and medulla) Pancreas (islets of Langerhan) Ovaries (female) Testes (male)

• Maintain homeostasis • Control reproduction • Promote smooth, sequential growth and development • Regulate RBC production • Digestion and absorption • Stress response - fight or flight

The control of the hypothalamus over the release of hormones of the anterior and posterior pituitary glands

Via a vascular pathway, the anterior pituitary releases its hormones straight into the bloodstream when stimulated via hormones of the hypothalamus

Via a neural pathway, neurosecretory cells connect the two glands, have their cell bodies in the hypothalamus and secrete hormones when stimulated via APs

• Growth hormones • Gonadotrophic hormones • Adrenocorticotrophic hormones Trophic - regulate the secretion of hormones of another gland

Vasopressin and oxytocin

Via negative feedback systems

• HYPOsecretion - not enough hormone, may be due a problem with the gland (primary) or with the hormone itself (secondary) • HYPERsecretion - too much hormone, may be due to tumours (primary) or with the hormone itself (secondary) • Target cell hyporesponsiveness - decreased number of receptors or impaired function, does not allow the target cell to respond adequately to hormones (eg. insulin resistance)

High levels of ADH despite normal circulating blood volume and serum osmolality - causes fluid acculumation

• Cancers • Trauma • Infection of the CNS • Drugs

Serum hyposomolarity and hyponatraemia (Na<135mmol/L) Thirst Nausea Fatigue Headache Vomiting Lethargy Dyspnea Seizures, loss of consciousness (cerebral oedema), respiratory arrest (Na+<115mmol/L)

• Correction of underlying problem • Emergency correction of severe hyponatraemia - GIVE SALT SLOWLY, otherwise can cause seizures and cerebral oedema, rise in ICP • Diuretics to aid fluid removal • Fluid restriction and daily weighs

Neurogenic: Caused by insufficient amounts of ADH despite low plasma volumes and high serum osmolality Nephrogenic: Caused by an inadequate response by the renal collecting tubules to ADH

• Brain tumours • Neurosurgery • Increased ICP • CNS infections

• Genetic abnormalities - Disorders and drugs that damage renal tubules

• Serum osmolarity • Polyuria • Nocturia • Extreme thirst and polydipsia • Hypovolaemia/hypotension • Poor skin turgor, dry mucous membranes • Confusion, irritability

• ADH replacement with desmopression aceteate/vasopression - Fluids - oral or IV

Increased levels of T3 and T4 (thyroid hormones)

Primary = excess thyroid hormone made and secreted by the thyroid gland. Caused by Graves disease, goiters, follicular adenoma, thyroid medications in excess

Excessive thyroid stimulating hormone production (TSH) Caused by TSH-secreting pituitary adenomas

Autoimmune disease T cells stimulate B cells to produce IgG ABs specific to TSH receptors ABs bind to TSH receptors in the thyroid = stimulate synthesis and secretion of thyroid hormone