Lecture 20 Flashcards
Hypothalamus gland
Control Center
Pituitary gland
Directed by the hypothalamus to secrete hormones to control endocrine gland function
Thyroid gland
Metabolism, growth
Parathyroid gland
Mineral regulation (Ca, P)
Adrenal glands
Metabolism/blood pressure
Pancreatic islets glands
Glucose regulation
Ovaries and testes glands
Sex, reproduction
Pineal glands
Sleep – melatonin
Autocrine
Cell products act on itself
Paracrine
Localized action around the production site (short distance)
Endocrine
Products secreted into bloodstream to have action at distant sites (long distance)
When are hormones synthesized?
In response to levels of hormone in circulation (pituitary hormones), or in response to levels of substances in the blood (glucose)
Negative feedback
Increased levels stimulate decreased production (pituitary hormones)
What do clinical disorders of endocrine glands result in?
Hyper or hyposecretion of hormones caused by gland abnormalities or abnormality in gland activity
Which lobe in the pituitary gland is vestigial in humans?
Intermediate lobe: Rudimentary structure
What is prolactin secretion controlled by?
Prolactin Inhibitory factor
What does thyroid stimulating hormone stimulate?
The release of prolactin and thyroid hormones
What causes hormone levels to fluctuate?
Natural (causes more hormones to be produced/pulsed), emotion, stress, anger, and fear
Growth hormone(GH) - Anterior PG hormone
Stimulates growth of tissues
Prolactin - Anterior PG hormone
Stimulates milk production
Thyroid-stimulating hormone (TSH) - Anterior PG hormone
Stimulates secretion of thyroid hormones
Adrenocorticotrophic hormone (ACTH) - Anterior PG hormone
Simulates release of adrenal hormones
Follicle-stimulating hormone (FSH) and Luteinizing hormone (LH) - Anterior PG hormone
Regulate sexual growth/development, fertility
Antidiuretic hormone (ADH) - Posterior PG hormone
Causes more concentrated urine (increased water reabsorption) – regulated in response to sodium ion conc in blood (detected by receptors in hypothalamus)
Oxytocin - Posterior PG hormone
Stimulates uterine contractions and milk secretion
Panhypopituitarism
The anterior lobe fails to secrete all hormones and Can be caused by tumor/destruction, neurologic injury, ischemia from reduced blood supply or rare congenital defects
Hypofunction of the anterior PG
Can lead to Pituitary dwarfism (deficiency of growth hormone, with stunted growth and development (can supplement with GH)
Hypofunction of the posterior PG
Can also lead to Diabetes insipidus from failure of posterior lobe to secrete ADH - inability to absorb H2O causes excretion of large amounts of diluted urine (supplement with ADH, increased fluid intake)
Functional pituitary gland tumours
Produce hormones that cause clinical manifestations (most commonly affects growth hormone and prolactin production)
Nonfunctional pituitary gland tumours
Do not produce hormones but exert other effects from tumour encroachment
Pituitary Gland Tumors treatment
Drugs can be used to suppress tumor growth, Excess hormone can be counteracted with inhibitor drug, and Surgical resection: Usual surgical approach is through the nasal cavity (transsphenoidal resection)
Pituitary Gland Hormone Overproduction
Overproduction of growth hormone, caused by pituitary adenoma and causes gigantism
Acromegaly
Adult onset of pituitary gland growth hormone overproduction. Since bones are no longer growing – they thicken and coarsen, Large jaws, and large, thickened fingers – not taller. It May cause visual disturbances, headaches, and neurological deficits. Curable with surgery
Prolactin overproduction
Result of small pituitary adenoma and or conditions affecting function of hypothalamus. Stimulates galactorrhea (milk secretion from breasts of women who are not pregnant) and inhibits FSH/LH, curable with surgery
Anovulation/amenorrhea
Loss of menstrual periods and in males – infertility, hypogonadism, sexual dysfunction
Thyroid Gland
Two lateral lobes connected by isthmus and composed of thyroid follicles that produce colloid and store hormones. It produces thyroid hormone T3 (triiodothyrine) and T4 (thyroxin) and controls the rate of metabolic processes
Colloid
Precursor thyroid hormones (thyroglobulin, T1,T2)
Goiter (causes + treatment)
Enlargement of the thyroid gland (non-toxic goiter: no increase in thyroid hormone). Enlargement is in response to TSH stimulation due to insufficient thyroid hormone.
Causes: Iodine deficiency (required to produce T3, T4 hormones), Enzyme deficiency or inefficient enzyme function– unable to produce hormones, and increased hormone requirements (puberty, pregnancy, stress)
Treatment: Administer thyroid hormone and suppress TSH or surgery
Hyperthyroidism
Excess secretion of thyroid hormone and can be caused by thyroid adenoma, most commonly by Graves disease (autoimmune disease), or antithyroid antibody. Can move eyes forward due to swelling from T-cells that attack fat, connective tissue and muscles.
Treatment: Antithyroid drugs, thyroidectomy of portion of thyroid, large doses of radioactive iodine, to destroy part of thyroid gland
Myxedema
Causes metabolic slowing, high levels of TSH and low levels of thyroid hormones
Treatment: administration of thyroid hormone
Cretinism
Caused by failed thyroid gland development or thyroid enzyme deficiency; only noticed months after birth. Causes impaired growth and impaired central nervous system development
Chronic Thyroiditis
Inflammation; Thyroiditis can be caused by acute viral or bacterial infection
Hashimoto Thyroiditis
Autoantibodies and T cells destroy thyroid tissue and TSH receptors (Graves – autoimmune stimulates) which causes decreased thyroid hormone production and an enlarged thyroid gland.
Treatment: administration of thyroid hormone
Thyroid Tumors
Typically present as benign adenomas (glands) but may progress to malignancy. These can also be a side effect of cancer treatments (5-10 year latency period)
Types of thyroid carcinomas
- highly-differentiated follicular and papillary carcinoma (Assoc with radiation exposure in children) - good prognosis in young
- Poorly differentiated follicular carcinomas – closely resembles thyroid tissue - poor prognosis
- Undifferentiated (anaplastic) carcinoma - uncommon and seen in older adults - poor prognosis
Medullary carcinoma (calcitonin secreting parafollicular cells)
Rare, secretes increased calcitonin (unregulated). Causes poor bone health (calcium scavenging), kidney stones, heart/ brain effects
How is Parathyroid hormone secretion regulated?
In response to blood calcium levels (high – decrease/ low – increase) tightly regulated: need to be kept in narrow range
Hyperparathyroidism
Relatively common disease that is usually caused from a hormone-secreting parathyroid adenoma, excess calcium in the body
Hypercalcemia (effect of hyperparathyroidism)
Blood calcium rises
Renal calculi (effect of hyperparathyroidism)
Excessive calcium excreted in urine
Secondary Hyperparathyroidism
Can result from chronic renal disease when too much calcium is lost
Tertiary Hyperparathyroidism
Chronic hyperparathyroidism (over 2y) – parathyroid becomes unresponsive to chronic low blood calcium levels and releases PTH constantly
Hypoparathyroidism causes + treatment
Usually from accidental removal of parathyroid glands, blood supply to glands during thyroid surgery/ treatment of goiter, or from autoimmune disease/congenital abnormality (Can cause seizures, irregular heart rhythms, and respiratory spams/failure)
Treatment: Raise calcium levels
Hypocalcemia
Blood calcium falls precipitously
Adrenals (+hormones secreted)
Paired glands above kidneys – two set of adrenal glands (inner – medulla, outer- cortex)
3 main hormones secreted:
1. Glucocorticoids: raise blood glucose (ACTH)
2. Mineralocorticoids: regulate electrolyte and water balance
3. Gonadocorticoids: Sex hormones (ACTH)
Addison Disease
An adrenal cortical hypofunction caused by atrophy or destruction of adrenal glands which results in a deficiency of all steroid hormone production (causes absent or irregular menstrual cycle)
Treatment: Administration of corticosteroids
Glucocorticoid deficiency
Hypoglycemia
Mineralocorticoid deficiency
Low blood volume and low blood pressure
Cushing Disease
Hyperfunction - excessive production of adrenal corticosteroids resulting in disturbed carbohydrate, fat, and protein metabolism (elevated blood glucose), increased breakdown of proteins, high blood pressure, blood volume, and osteoporosis
Most common causes of Cushing Disease
ACTH Hormone-producing pituitary microadenoma (Cushing disease – most common), Corticosteroid -producing adrenal cortex adenoma, Hyperplastic adrenal glands or tumor (secreting ACTH)
Congenital adrenal hyperplasia (CAH) (over production of adrenal sex hormones)
Deficiency of enzymes required for synthesis of aldosterone/cortisol, Early sexual development in males – stunted development of puberty in females (virilization/masculinization, ambiguous genitalia, infertility), and hypoglycemia, elevated BP
Overproduction of aldosterone
Promotes absorption of salt and water in kidneys and elimination of potassium
Adrenal Medulla
Produces catecholamines that stimulate the sympathetic nervous system, Norepinephrine (noradrenaline), Epinephrine (adrenaline)
Pheochromocytoma
Rare tumor (benign) that results in increased secretion of catecholamines (large amounts) which may cause cerebral hemorrhage from hypertension; inherited susceptibility (gene mutations in MEN1 and 2
Nonendocrine Tumors
Can secrete hormones like molecules. Ex: Ectopic hormones: Hormones secreted by nonendocrine tumors that are identical with or mimic action of true hormones (ACTH, TSH, gonadotropins, ADH, PTH and insulin) - found in humors of the lung, pancreas, kidneys, and connective tissue
Pancreatic Islets (Islets of Langerhans)
Produces hormones – glucose regulation/digestion
Beta cells: Insulin production – glucose metabolism (in response to high blood glucose)
Alpha cells: Glucagon – raises blood glucose and fatty acid concentration
Delta cells: Somatostatin reduces acid secretion (digestive system)
Gonads (Ovaries, Testis) function
- Production and development of germ cells (sperm or ovum) - required for sexual development/fertility
- Endocrine function: Production of sex hormones: (testosterone, progesterone, estrogen)
Homeostasis
Maintenance of steady state in internal control system – can be affected by stress and its impact on the endocrine system
Acute stress response
Fear, fight, flight – mediated by sympathetic NS though the adrenal medulla (Epinepherine/norepinepherine)
