Endocrinology Flashcards
What is endocrinology?
The study of hormones
What is a hormone?
Secreted directly into the blood by discrete specialised cells in response to a sepecific stimulus.
The amounts vary with teh strength of the stimulus and transported to distant target where it exerts special effects.
What are endocrine glands?
Responsible for hormone production, secreting into bloodstream.
Other organs can produce it.
What are the endocrine glands?
Hypothalamus
Pituitary
Parathyroid glands
Thyroid gland
Adrenal glands
Pancreas
Ovaries/testis
Also stomach, small intestines, adipose tissue and kidney
What is the reproduction axis?
Hypothalamus - GnRH
Anterior pituitary - FSH/LH
Target organ gonads - Androgens, oestrogens and progestins
Effect - reproduction
What is the growth axis?
Hypothalamus - GnRH (+) and Somatostatin (-)
Anterior pituitary - GH
Target organ Liver - IGF - 1
Growth
What is the metabolism axis?
Hypothalamus - TRH (+) and Somatostatin (-)
Anterior pituitary - TSH
Target organ thyroid - Thyroid hormones
Metabolism
What is the milk production axis
Hypothalamus - TRH (+) and DA (-)
Anterior pituitary - Prolactin
Mammary gland
Milk production
What is the inflammation axis?
Crh
ACTH
Adrenal cortex - glucocorticoids
Inflammation/metabolism
How are hormones classified?
Proteins/peptide hormones
Steroid hormones from cholesterol
Amino acid derivatives
FA derivatives
What are examples of protein and peptide hormones?
Insulin and LH
What are examples of steroid hormones?
Cortisol and oestradiol
What are examples of amino acid derived hormones?
Thyroxine and norepinephrine
What are examples of fatty acid derived hormones?
Prostaglandins and leukotrienes
What are details of protein and peptide hormones?
Vary in size
Peptide hormones - only a single chain of AA
Protein hormones - larger chains of AA or peptide chains
Stored in secretory vesicles until needed
What are examples of peptide hormones?
Thyrotropin releasing hormone - only 3AA residues
Gonadotrophin releasing hormone - 10AA
What are glycoprotein peptide hormones?
Large molecules that are glycosylated, often with two distinct peptide chains (alpha and beta) joined by non-covalent bonds
What are examples of glycoprotein peptide hormones?
Gonadotrophin - LH and FSH
Thyroid stimulating hormone
Both from anterior pituitary
What are steroid hormones?
A large class of lipids, synthesied mainly in adrenal cortex, testis, ovary and placenta
Precursor is cholesterol
Common ring structure, 3 6-membered rings and a 1 5-membered ring.
What are hormones derived from amino acids?
Adrenaline
Noradrenaline
Dopamine
Thyroid hormones: thyroxine and triiodothyronine (both from tyrosine)
What are hormones from fatty acids?
Eicosanoids, two major classes:
- Prostaglandins
-Leukotrienes
Derived from aracidonic acid, with short half life so act near site of synthesis
What are prostaglandins?
Formed in most tissues of body, type depends on down stream enzyme present.
PGD2, PGE2, PGF2a, PGI2 and TXA2
e.g. uterus - in implantation and parturition
seminal vesicles - sperm motility
How do hormones exert their effects?
Binding to a receptor either on cell surface or intracellular
What is gonadotrophin releasing hormone?
10 AAs
Synthesised in the hypothalamus
Derived from post-translation modification of precursor molecule
Secreted in pulsatile manner
Half life is 7mins in eyes
Leads to gonadotrophin release
What are the gonadotrophin hormones?
LH and FSH are glycoproteins
Secreted by anterior pituitary
LH - half life of 30 mins
FSH - half life of 3-4 hours
What does FSH lead to ?
Males - sperm production by testes and forms of oestradiol (sertoli cells)
Females - growth and maturation of follicle, ova production and secretion of oestradiol (granulosa cells)
What does LH lead to?
Males - stimulates secretion of testosterone by testes (leydig cells)
Females - with FSH stimulates oestradiol synthesis and ovulation. Stimulates formation of CL and progesterone secretion.
What steriod hormones do the gonads produce?
Progestins (progesterone)
Oestrogens (oestradiol)
Androgens (testosterone)
How are steroid hormones produced?
Cholesterol -> Progestins -> Androgens -> Oestrogens
