Endocrine System Flashcards
Growth hormone
It is secreted by somatotrophs of anterior pituitary.
∆ Actions
1) Effect on growth
A) Skeletal growth
Growth of long bones by growth of epiphyseal cartilage by
i) Proliferation of chondrocytes and osteogenic cells.
ii) laying down more bone matrix and more chondroitin sulfate.
iii) conversion of chondrocytes into osteogenic cells.
iv) conversation of proline to hydroxy proline forming collagen.
B) Soft tissue growth
Causing hypertrophy and hyperplasia of cells. Causes growth of muscles and organs like liver and stomach.
2) Effects of metabolism
1) Protein metabolism -
-Increase amino acid transport in cells
-stimulate transcription of DNA and mRNA translation.
-decreases breakdown of protein and has anabolic effect on proteins.
2) Carbohydrate metabolism -
-GH decrease glucose utilisation by increasing FFA utilisation.
-promotes glycogen deposition
-decreases glucose uptake by cells producing hyperglycemia effects.
3)Fat metabolism
-Stimulate lipolysis and FFA utilisation
-sparing action on proteins and glucose.
- promotes formation of acetoacetic acid.
∆ MECHANISM OF ACTION
-direct action on protein synthesis and fat metabolism
- action of bones and soft tissues is by somatomedins.
- 4 somatomedins A,B,C,D of which somatomedin C is called Insulin like growth factor.
∆ REGULATION
-Growth hormone releasing hormone which promotes release of GH.
-Growth hormone inhibiting hormone
These are transported to anterior pituitary through hypophyseal portal vessels.
∆Applied aspects
1) Hypersecretion of GH before fusion of epiphyseal plates lead to gigantism and after fusion leads to acromegaly.
2) Hyposecretion produce dwarfism in children and simonds disease in adults.
Cushing syndrome (hyperadrenalism)
Cause- excess secretion of cortisol due to cortisol secreting tumor.
Features-
1) Fat with central obesity like fat deposited in face - moon face and fat deposited in upper back which is buffalo hump.
2) Loss of protein from muscles and wasting of proximal limb muscles.
3) Lymphopenia and poor immune system with poor wound healing.
4) Hyperglycemia causing adrenal diabetes mellitus
5) Hypercalcaemia and multiple fractures.
Treatment - Surgical removal of tumor.
Addisons disease (Hyposecretion of cortisol)
Causes
1) Formation of autoantibodies against adrenocortical cells.
2) Decreased ACTH from anterior pituitary
3) adrenocarcinoma
Features-
1) Pigmentation of skin and mucus membrane.
2) Frequent attacks of dizziness and fainting due to hypoglycemia.
3) Inability to tolerate stress and tension.
4) Associated mineralocorticoid deficiency causing postural hypotension, Na depletion and K retention.
5) Decreased vascular responsiveness to circulating catecholamines.
6) Increase in neutrophil and eosinophil count.
Hyperparathyroidism
Excess secretion of parathyroid hormone.
Causes
1) Adenoma of parathyroid chief cells
2) Carcinoma
3) Vit. D deficiency
4) Dietary Ca deficiency
Features
1) Commonly present in females.
2) Excess bone resorption and osteoporosis - osetoclastic activity
3) Increased serum Ca levels producing depression of CNS and PNS.
4) Hypercalcaemia reduces response to ADH leading to thirst, weakness and constipation.
5) Increased incidence of renal calculi.
6) Shortening of QT interval.
Hyperthyroidism
Thyrotoxicosis due to Hypersecretion of thryoid hormones due to thyroid stimulating antibodies which combine with TSH receptors on thyroid gland and activate them leading to graves disease.
Features
1) Rise in body temperature and BMR, excessive sweating.
2) Exopthalmos- protrusion of eyeballs with dryness and infection of cornea and conjuctiva.
3) Loss of weight and increased GI motility leading to diarrhea.
4) Increased cardiac output and arrhythmias.
5) Fatigue and insomnia
6) excess breakdown of muscle proteins myopathy, leading to muscle wasting
Diagnosis is confirmed by high levels of T3 AND T4 and low levels of TSH.
Cretinism
Due to decreased secretion of thyroid hormones due to
1) congenital absence of thyroid gland
2) Genetic defect in thyroid hormone synthesis.
3) Lack of iodine in diet
4) Disease affecting TSH and TRH levels.
Features
1) Retardation of physical growth with dwarfism
2) Mental retardation due to failure of neural growth.
3) Delayed puberty and sexual growth decreased.
4) Child has idiotic bloated face, thick lips and enlarged protruding tongue,
5) Abdomen is pot belly
6) Reduces BMR
7) Reduced appetite with decreased GI motility
Diagnosis - Decreased T3 and T4 levels and increased TSH levels.
Tetany (Hypoparathyroidism)
It is sustained contraction or spasm of muscles due to lowered serum Ca levels.
Causes
1) Vitamin D deficiency or rickets
2) Intestinal spure
3) Chronic renal failure
4) Alkalosis
Clinical features -
1) Carpopedal spasm- spams of flexor muscles of hand producing flexion at wrist and metcarpophalyngeal joint.
2) Trosseaus sign - same as above but occurs after tying sphygmomanometer
3) Laryngeal stridor or crowing sound due to spasm of laryngeal muscles.
4) Chvosteks sign - Tapping of facial nerve causing spasm of ipsilateral facial muscles.
Acromegaly
Hypersecretion of growth hormone in adults after fusion of epiphyseal plates.
Features
1) Enlargement of hands and feet. Finger and toe bones become thick due to periosteal bones.
2) Excessive growth of lower jaw which protrude forwards(prognathism).
3) Enlargement of skull , cheeks and frontal bones producing frontal bossing.
4) Enlargement and widening of nose.
5) Enlarged tongue
6) Gorilla like face
7) Headache and visual disturbance due to bitemporal hemianopia
8) X-ray of skull shows Enlargement of sella tursica.
Diagnosis is confirmed by increased levels of growth hormones and somatomedin levels.
Gigantism
Hypersecretion of growth hormone in childhood before fusion of epiphyseal plates.
Due to increased activity of somatotrophs of anterior pituitary or tumor.
Features-
1) Talk stature
2) Deformities of chest wall and spine abnormalities like kyphosis.
3) Hand and foot size increased
4) Thick skin and splenomegaly, hepatomegaly, renomegaly.
5) Hyperglycemia causing exhaustion of insulin
6) Headache and visual disturbance due to bitemporal hemianopia.
7) X-ray of skull shows Enlargement of pituitary fossa.
8)
Diabetes insipidus
Occurs due to reduced secretion of anti diuretic hormone due to
1) Trauma to hypothalamus
2) Tumor
3) Thrombosis of blood vessel supplying hypothalamus.
Features.
1) Polyuria- passing large volume of urine.
2) Intense thirst and drinking large quantity of fluids.
3) Dilute urine with low specific gravity.
4) Water deprivation test fails to increase osmolarity of urine.
5) Non availablity of water increases risk of fatal dehydration.
Oxytocin
Secreted by supraoptic nucleus of hypothalamus.
Actions:
• Milk ejection reflex - sucking is stimulus.
• Contraction of uterus at time of delivery.
• After delivery maintain uterus in sustained contracted state and stops bleeding.
• In males it causes contraction of myoepithelial cells of seminiferous tubules.
Myxoedema
Hyposecretion of thyroid hormones in adults.
Causes
• Common in females
• Face and body has puffy oedematous look.
• Bradycardia and decrease in cardiac output.
• Fatigue and loss of memory
• Decrease in BMR by 40-50%
• Skin becomes coarse and dry and yellow skin(carotinemia).
• Appetite is reduced and weight gain occurs.
• Disturbance in menstrual cycle.
Glucagon
Secreted by alpha cells of islets of langerhans.
Action:
• Glycogenolysis in liver causing release of glucose in blood.
• Stimulates gluconeogenesis by conversion of pyruvate into PEP.
• Promotes lipolysis in adipose tissue.
• Stimulates strength of myocardial contraction.
• Stimulates bile secretion.
Regulation:
• Fall in blood glucose level inhibit glucagon secretion.
• Increase in amino acid level stimulates glucagon secretion.
• Execrise stimulates glucagon secretion.
• Insulin inhibits glucagon secretion.
Primary hyperaldosterism or conns syndrome
It occurs in conditions like adrenal adenoma or hyperplasia of zona glomerulosa.
Features:
• Hypokalemia
• Hypokalemia depress action potential formation and causes muscle paralysis.
• Polyuria
• Metabolic alkalosis with acidic urine
• Mild hypertension
• Low plasma renin levels
Secondary hyperaldosterism
In this there is excess secretion of aldosterone along with renin.
It occurs due to
• Congestive cardiac failure
• Renin secreting tumor in kidney
• Liver cirrhosis
• Nephrotic syndrome
