Hormones 1

What is a hormone?

A hormone is a substance secreted directly into the blood via specialised cells, in response to a particular stimulus.

What are the major endocrine glands?

Hypothalamus

Posterior/anterior pituitary glands

Thyroid glands

Adrenal glands

Parathyroid glands

Thymus

Pancreas

Gonads (testes/ovaries)

What are the major hormones?

Oxytocin

ADH

Thyroid

Cortisol, aldosterone and adrenaline

Parathyroid hormones

Thymosin

Insulin and glucagon

Testosteroene and oestradiol/progesterone

What endocrine hormones function?

Hormones that are secreted directly into the blood stream where they are transported

What is a paracrine hormone?

Hormone released by a gland cell into extracellular space, to a target cell within the gland

What does an Autocrine hormone do?

Released by a cell and acts on the same cell

How does a neuroendocrine hormone function?

Neuronal hormone that is released into synaptic cleft for target cell

How are protein/peptide hormones synthesised?

Preprohormone in rER is cleaved forming a prohormone

The prohormone is then cleaved in secretory vesicle to produce the hormone which can be released via exocytosis

What is the structure of glycoprotein hormones?

Contain two peptide chains linked via non-covalent bonds

Alpha subunit is common to LH, FSH and TSH the beta subunit determines specifics

Glycosylated

How do protein/peptide hormones act?

Bind to cell surface receptors and cause downstream signalling

what are steroid hormones and synthesis basics?

Lipid hormones synthesised from cholesterol by steroidogenic

Mainly produced in gonads, adrenal cortex

How do steroid hormones act?

Transported in the blood bound to carrier proteins

Bind to cytoplasm/nuclear receptors, dimerise and regulate transcription

What are examples of catecholamines?

Include adrenaline, noradrenaline and dopamine

How do catecholamines act?

Bind to GPCRs

Specific G-proteins can either inhibit/activate signalling pathways

What are eicosanoids?

Derived from phospholipids which are converted to arachidonic acids

AA is converted to either prostaglandins or Leukotrienes

These bind to GPCRs

Which hormones travel freely in blood and which are protein bound?

Peptide and catecholamines are free

Steroid and thyroid hormones are protein bound