Endocrine Biomed Capstone

What causes hyperthyroidism

overstimulation of thyroid producing excess thyroid hormones. graves disease, multi-nodular goitre, pituitary tumour, increased T3

What causes hypothyroidism

chronically low plasma TH levels

Two types of hypothyroidism

Primary (thyroid gland problem) = low T3 + T4, HIGH TSH (caused by iodine deficiency, hashimotos disease)

Secondary (anterior pituitary problem) = low T3, T4, TSH

TSH and impact on thyroid function

Primary hypothyroidism -> Increase TSH -> Decrease T3 + T4

Secondary hypothyroidism → decrease TSH → decrease T3 + T4

Hyperthyroidism -> Decrease TSH -> Increase T3 + T4

TSH impact on follicles

Increase T3 + T4 -> Decrease TRH + TSH -> follicles shut down

Decrease T3 + T4 -> TSH secretion -> follicles activated

Cushings syndrome pathology

caused by high blood cortisol, adrenal hyperplasia due to excess ACTH stimulation from anterior pituitary due to pituitary neoplasms

Cushings syndrome symptoms

Increased fat + redistribution to central areas, increased protein breakdown + gluconeogenesis, muscle wasting, hyperglycemia

Addisons vs Cushings disease

Addisons = adrenal HYPOfunction

- low cortisol, hypoglycaemia, weight loss

Cushings = adrenal HYPERfunction

- high cortisol, hyperglycaemia, weight gain

Iodine degrades TG into T3 + T4

1. TSH binds to receptor -> TG synthesised in apical membrane + secreted into colloid

2. TG is iodinised and translocates back into apical membrane

3. Endocytosis + degradation of TG into T3 + T4 occurs

4. T3 + T4 released to peripheral tissues

How does iodine deficiency cause a goiter

Without iodine degrading TG into T3 + T4, TSH overstimulation occurs to compensate for decrease in circulating T3 + T4. Causes thyroid to enlarge = goiter

Regions of the adrenal gland

Adrenal Cortex = Corticosteroids

• Zona Glomerulosa = mineralocorticoids

• Zona Fasciculata = Glucocorticoids

• Zona Recticulans = Gonadocorticoids

Adrenal Medulla = catecholamines (adrenaline, noradrenaline, dopamine)

Conn's disease

primary hypoaldosteronism, condition where the adrenal glands produce too much of the hormone aldosterone

pathology = increased blood pressure, decreased potassium, decreased H+ (alkalosis)

Hypersecretion of growth hormone can lead to 2 disorders based on timing of hypersecretion :

If hypersecretion occurs during childhood = gigantism

If hypersecretion occurs during adulthood = acromegaly (thickening of features)