Parathyroid Gland to Adrenal Gland

Parathyroid Gland

• A gland that regulates calcium levels, It is located on or near the thyroid capsule (region of the thyroid gland) sometimes within the thyroid gland.

• It may also be found outside their normal anatomic site – between the hyoid bone in the neck and mediastinum.

• Smallest endocrine gland in the body

TRUE

TRUE OR FALSE

Most people have 4 parathyroid glands but some have 8 or as few as 2.

Parathyroid Hormone (PTH)

Secreted by the chief cells of parathyroid glands as a Polypeptide, it increases blood calcium levels by promoting bone resorption, activating vitamin D, and stimulating intestinal calcium absorption.

If Calcium Levels Decrease, PTH is released

Oxyphil cells

Cells of no known function

Parathormone or Parathyrin

Other name of Parathyroid hormone

84

How many Amino acids do Parathyroid Hormone contain.

FALSE

TRUE OR FALSE

Parathyrin acts to decrease calcium concentration, whereas calcitonin acts to increase the concentration of calcium (Ca2+) in the blood.

4 minutes

PTH approximate Half-life

9.4 kDa

PTH Molecular Mass

PTH Regulation of Serum Calcium

• Bone- enhances the release of calcium from the large reservoir contained in the bones.

• Kidney- enhances active reabsorption of calcium and magnesium from distal tubules and the thick

  ascending limb.

• Intestine via Kidney- enhances the absorption of calcium in the intestine by increasing the production of

  activated vitamin D.

PTH Regulation of Serum Phosphate

PTH reduces the reabsorption of phosphate from the proximal tubule of the kidney which means more phosphate is excreted through the urine.

PTH role in Vit D synthesis

PTH increases the activity of 1-α-hydroxylase enzyme, which converts 25-hydroxycholecalciferol to 1,25 dihydroxycholecalciferol, the active form of vitamin D.

Hyperparathyroidism

Excessive production of parathyroid hormone leading to hypercalcemia, with primary, secondary, and tertiary forms having different causes and effects.

Primary Hyperparathyroidism

• Physiologic effect lies with the PT gland

• Most common cause of hypercalcemia

• Due to the presence of a functioning parathyroid adenoma

• Accompanied with phosphaturia

• If it is undetected, severe demineralization may occur

Secondary Hyperparathyroidism

• Develops in response to serum calcium

• There is diffuse hyperplasia of all 4 glands

• The patient develops severe bone disease

• Causes: vitamin D deficiency and chronic renal failure

Tertiary Hyperparathyroidism

• It occurs when patients with secondary hyperparathyroidism

• Develop autonomous function of the hyperplastic parathyroid glands or of a parathyroid

  adenoma

• The phosphate levels are normal to high; calcium phosphates in soft tissue

Hypoparathyroidism

• Individuals are unable to maintain calcium concentration in blood without calcium supplementation

• Due to accidental injury to the PT glands during thyroid or neck surgery, removal of the glands with

  thyroid glands, or idiopathic atrophy

• Other cause: autoimmune parathyroid destruction

Adrenal Gland

• Endocrine glands located atop the kidneys

• In humans, the right suprarenal gland is triangular shaped, while the left suprarenal gland is semilunar shaped.

• Comprising the adrenal cortex (Outer and Yellow) and adrenal medulla (Dark Mahogany), responsible for releasing hormones in response to stress.

Suprarenal Glands

Other name of Adrenal Gland

Functions of Adrenal Glands

• They are chiefly responsible for releasing hormones in response to stress.

• through the synthesis of corticosteroids such as cortisol and catecholamines such as epinephrine.

• The adrenal glands affect kidney function through the secretion of aldosterone, a hormone involved in

  regulating the osmolarity of blood plasma.

Adrenal Corterx

• Outer region of the adrenal gland secreting the steroid hormone.

• Major site of steroid hormone production.

Zona Glomerulosa

• Most Superficial Cortical Layer

• Mineralocorticoids (Aldosterone)

Zona fasciculate

• Middle cortical layer

• Glucocorticoid (Cortisol)

Zona reticularis

• Deepest cortical layer

• weak androgens

Mineralocorticoids

• The primary mineralocorticoid is aldosterone (most potent – electro regulating hormone).

• Its secretion is regulated by the oligopeptide angiotensin II (angiotensin II is regulated by angiotensin I, which in turn is regulated by renin).

Aldosterone effects on metabolism

• It increases urinary excretion of potassium ions

• It increases interstitial levels of sodium ions

• It increases water retention and blood volume

Primary hyperaldosteronism (Conn’s disease)

• Caused by Aldosterone-secreting adrenal adenoma

• Symptoms: HPN, hypokalemia, mild hypernatremia and metabolic alkalosis.

Secondary hyperaldosteronism

Occurs as a result of excessive production of rennin

Bartter’s syndrome (Bumetanide-sensitive chloride channel mutation)

• Elevated concentrations of Aldosterone and rennin

Gitelman’s syndrome (Thiazide-sensitive transporter mutation)

• Increased aldosterone

Liddle’s syndrome (pseudohyperaldosteronism)

• resembles primary aldosteronism

• clinically but aldosterone level is low and absence of HPN

Hypoaldosteronism

• Due to destruction of the adrenal glands and deficiency of glucocorticoid.

• It is also associated with enzyme 21-hydroxylase deficiency.

• Symptoms: hyperkalemia and metabolic acidosis.

Glucocorticoids

• Hormones produced in the adrenal cortex, like cortisol, influencing metabolism, immune response, and stress adaptation.

• Its secretion is regulated by the hormone ACTH from the anterior pituitary.

TRUE

TRUE OR FALSE

Glucocorticoids are high in early morning (6-8am), lowest at night (10-12am).

Cortisol effects in Metabolism

• It stimulates the release of amino acids from the body

• It stimulates lipolysis, the breakdown of fat

• it stimulates gluconeogenesis, the production of glucose from newly-released amino acids and lipids – resulting in hyperglycemia (anti-insulin effect)

• It increases blood glucose levels in response to stress, by inhibiting glucose uptake into muscle and fat cells

• It strengthens cardiac muscle contractions

• It increases water retention

• It has anti-inflammatory and anti-allergic effects

Androstenedione (Andro)

An androgenic steroid produced by the testes, adrenal cortex, and ovaries, serving as a precursor to testosterone and other androgens, as well as the parent structure of estrone.

Hypercorticolism (Cushing’s syndrome)

• Is cause primarily by excessive production of cortisol and ACTH

• Signs and symptoms: weight gain but with thin extremities (buffalo hump), hyperglycemia, thinning of the skin, poor wound healing, HPN, decreased WBC

Primary Hypocorticolism (Primary Adrenal Insufficiency)

• Due to decreased cortisol production – 90% destruction of the adrenal cortex, Aldosterone deficiency, excess ACTH release

• Disorders: Addison’s disease – hypotension, Hyponatremia, hyperkalemia, hyperpigmentation and darkening of the skin

Secondary and Tertiary Hypocorticolism

• Due to hypothalamic-pituitary insufficiency with loss of ACTH.

• No problem with mineralocorticoid secretion; absence of hyperpigmentation.

Androgens

• Produce as by-product of cortical synthesis that are regulated by ACTH.

• They circulate bound to steroid hormone binding globulin (SHBG).

Testosterone

A hormone with a wide variety of effects, ranging from enhancing muscle mass and stimulation of cell growth to the development of the secondary sex characteristics.

Dihydrotestosterone (DHT)

A metabolite of testosterone, and a more potent androgen than testosterone in that it binds more strongly to androgen receptors.

Androstenedione (Andro)

An androgenic steroid produced by the testes, adrenal cortex, and ovaries. While androstenediones are converted metabolically to testosterone and other androgens, they are also the parent structure of estrone.

Dehydroepiandrosterone (DHEA)

The primary precursor of natural estrogens, also known as dehydroisoandrosterone or dehydroandrosterone, produced by the reticularis and sulfated by SULT2A1 by the action of sulfotransferase.

Adrenal Medulla

• It is located at the center of the gland, being surrounded by the adrenal cortex.

• consisting of hormone-producing chromaffin cells that secrete epinephrine (adrenaline), norepinephrine (noradrenaline), and a small amount of dopamine in response to stimulation by sympathetic preganglionic neurons.

• the principal site of the conversion of the amino acid tyrosine into the catecholamines epinephrine, norepinephrine, and dopamine.

Epinephrine (Adrenaline / Secondary Amine)

• A hormone and neurotransmitter

• Most abundant medullary hormone

• Called the “flight and fright hormone” because it is released in response to physiologic (injuries) or

  psychological (stress, anxiety) threats.

• Released in response to stress.

Functions of Epinepherine

• increasing heart rate

• constricting blood vessels

• dilating air passages

• mobilizing glucose for energy (Glycogenolysis)

"On the kidney"

The term adrenaline is derived from the Latin roots ad- and renes and literally means ?

Catecholamine

What is the Chemical property that makes epinephrine a monoamine produced only by the adrenal glands from the amino acids phenylalanine and tyrosine?

Norepinephrine (Noradrenaline / Primary Amine)

• A catecholamine acting as a hormone and neurotransmitter

• involved in the fight-or-flight response, increasing heart rate, glucose release, and oxygen supply to the brain.

Noradrenergic

Areas of the body that produce or are affected by norepinephrine are described as

An increase in norepinephrine from the sympathetic nervous system increases the rate of contractions

Role of norepinephrine as neurotransmitter

dopamine β-hydroxylase

Norepinephrine is synthesized from dopamine by

noradrenegic neurons in the locus coeruleus

Norepinephrine is released to the CNS and Sympathetic Nervous System by?

The binding to adrenergic receptors

The actions of norepinephrine are carried out via

Dopamine

A catecholamine produced from 3,4-dihydroxyphenylalanine (DOPA), mainly found in the brain, influencing attention and responses.

Enkephalin

Produced by chromaffin cells, regulating pain perception.

Pheochromocytoma

Tumors of the adrenal medulla or sympathetic ganglia leading to catecholamine overproduction, causing symptoms like tachycardia, tightness of chest, pallor and sweating.

Neuroblastoma

A malignant condition in children associated with excessive norepinephrine production under extreme stress.