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

TSH inversely related to thyroid gland activity

If primary hypothyroidism -> Increase TSH -> Decrease T3 + T4

If 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 (Thyroid Stimulating Hormone) binds to receptor leading to TG production

2. Iodine translocates to basolateral membrane to iodises TG

3. Promotes endocytosis then degradation into T3, T4

How does iodine deficiency cause a goiter

1. iodine iodises TG into T3 + T4 in follicular cells → without iodine → decrease in circulating T3 + T4

2. negative feedback to pituitary is reduced → pituitary secretes TSH

3. chronic TSH stimulation of follicles → follicular cells hypertrophy and hyperplasia → thyroid gland enlarges

Regions of the adrenal gland

Outer cortex = produces steroid hormones (glucocorticoids, mineralocorticoids, gonadocorticoids)

Inner Medulla = produces catecholamines (adrenaline, noradrenaline, dopamine)

Conn's disease

primary hyperaldosteronism. affects aldosterone producing adrenal adenoma of zona glomerulosa. 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)