Secondary endocrine functions

What are examples of organs with secondary endocrine functions?

Thymus gland, heart, kindeys, stomach, adipose tissue

Where is the thymus located?

Behind the sternum between the lungs

What hormones does the thymus secrete?

thymosin, thymic humoral factor, thymic factor, thymopoietin

What is the role of the thymus?

Stimulate T-lymphocyte production and maturation

What hormones does the GI tract secrete?

gastrin, secretin, cholecystokinin, glucose-dependent insulinotropic peptide

What is the function of gastrin?

promote the secretion of gastric juice and increase movements of stomach

What is the function of secretin?

Stimulate the secretion of pancreatic juice

What is the function of glucose-dependent insulinotropic peptide (GIP)?

stimulates release of insulin and reduce gastric secretion & intestinal motility

What is the function of cholecystokinin (CCK)?

stimulate secretion of pancreatic juice and release bile, cause full feeling after eating

What hormone does the stomach and small intestine secrete?

somatostatin

What does adipose tissue produce?

Leptin

What is the function of leptin?

acts on hypothalamus to suppress appetite

What are the levels of leptin in people with obesity?

Rich in leptin - ineffective due to mutation or hypothalamic cells lack receptors for leptin

What hormone does the heart secrete?

atrial natriuretic peptide (ANP)

What is the function of ANP?

Decreases BP and decreases reabsorption of sodium and water in renal tubules

What hormones does the kidneys produce?

renin, erythropoietin (EPO), calcitriol

When is erythropoietin released?

in response to low levels of oxygen in the blood (hypoxia)

What is the function of EPO?

stimulates RBC production in the bone marrow

What is the function of calcitriol?

aids in absorption of dietary calcium and phosphorus

What are prostaglandins?

local lipid hormones produced by most body tissues

What are features of prostaglandins?

• actions are short-lived

• quickly metabolised

• do not circulate in the blood to target organs

What are the functions of prostaglandins?

Inflammatory response

Pain

Fever

Regulate BP

Blood clotting

Uterine contraction during labour

vasoconstriction and vasodilation

How does aspirin affect prostaglandins?

Inhibits the synthesis of PGs involved in pain mechanism so reduced pain and fever

Blocks the synthesis of prostaglandins necessary for blood clotting

What are the functions of histamine?

Increases capillary permeability and vasodilation

Acts as neurotransmitter

Causing contraction of smooth muscle of bronchi and secretes gastric juices

Where is histamine synthesized and stored?

mast cells and basophils

What are the functions of serotonin?

intestinal secretion and contraction of smooth muscle

blood clotting homeostasis

affect mood

what are growth factors?

local hormones that stimulate cell growth and division, tissue development and growth

What do growth factors act as?

autocrine and paracrine

What causes hypersecretion of growth hormones?

Hormone-secreting pituitary tumour

What is the effect of the increasing tumour?

Compression of nearby structures leads to hyposecretion of other pituitary hormones - damage optic nerve and visual disturbances

What can hypersecretion of GH lead to?

gigantism, acromegaly

what is gigantism?

long bones grow excessively

height = 2.1-2.4m

what is acromegaly?

Bones become abnormally thick and large

Coarse facial features and excessive growth of lower jaw, hands and feet

Skin becomes thicker

Nerves compress

What is the treatment for hypersecretion of GH?

surgical removal of tumour or destruction by radiation

What can hyposecretion of GH lead to?

pituitary dwarfism

What is hyperprolactinaemia?

abnormally high levels of prolactin in the blood

What can hyperprolactinaemia lead to?

galactorrhoea, amenorrhea and sterility in women

What is panhypopituitarism?

deficiency of all anterior pituitary hormones

What are the causes for hyposecretion of anterior pituitary hormones?

tumours of the hypothalamus or pituitary

trauma or surgery

pressure caused by a tumour adjacent to the pituitary gland,

infection, e.g. meningitis, encephalitis, syphilis

What hormones decrease as you age?

human growth hormone, thyroid hormones, cortisol, aldosterone, oestrogens, androgens, calcitonin

what hormones increase as you age?

TSH, PTH, LH, FSH

What can decrease thyroid hormone lead to?

decreased metabolic rate, increased body fat, hypothyroidism, increased TSH levels

What can an increase in PTH and decrease in calcitonin lead to?

osteoporosis, fracture risk

What is the effect of age on pancreatic beta cells and insulin?

Beta cell function declines with age, insulin secretion decreases with age and receptor sensitivity to insulin declines. Blood glucose levels increase faster with age

What is the effect of age on the thymus?

after puberty thymus size decreases

What is the effect of age on the ovaries?

decreases in size with age and don't respond to gonadotropins, FSH and LH levels increase

What is the effect of age on the testes?

testosterone levels decrease