LMP299Y1 Lecture Notes - Lecture 7: Anterior Pituitary, Thyroid, Posterior Pituitary

21 views6 pages
Published on 12 Apr 2013
School
Course
Professor
Page:
of 6
LECTURE SEVEN: INTRODUCTION TO THE BIOCHEMISTRY OF HUMAN DISEASES
PRINCIPLE ENDOCRINE GLANDS
Brain region: (1) Hypothalamus; (2) Pituitary gland
Neck region: (1) Parathyroid glands; (2) Thyroid gland
Abdominal region: (1) Adrenal glands;(2) Pancreas
Groin region: (1)Ovaries (female);(2) Testes (male)
HYPOTHALAMUS
Releasing and Inhibiting Hormones (these are the hormones
that control the pituitary to secrete or inhibit certain
hormone production or secretion):
o Thyrotrophin-releasing hormone (TRH)
o Somatostatin
o Gonadotrophin-releasing hormone (GnRH)
o Corticotrophin-releasing hormone (CRH)
o Growth hormone-releasing hormone (GHRH)
o Prolactin-inhibiting factor (dopamine)
PITUITARY (the different sides of the pituitary (anterior or
posterior) produce different products these control the
peripheral endocrine glands to release certain hormones) (they
are made by the hypothalamus and then stored in the posterior
pituitary)
Anterior Pituitary:
o Thyroid-stimulating hormone (TSH)
o Luteinizing hormone (LH)
o Follicle-stimulating hormone (TSH)
o Growth hormone (GH)
o Prolactin (PRL)
o Adrenocorticotrophic hormone (ACTH)
Posterior Pituitary:
o Vasopressin or antidiuretic hormone (ADH)
o Oxytocin
THYROID (these are the peripheral endocrine glands):
o Thyroxine (T4)
o Triiodothyronine (T3)
o Calcitonin
PARATHYROID (these are the peripheral endocrine glands):
o Parathyroid hormone
ADRENAL
Adrenal Cortex:
o Mineralocorticoids (Aldosterone)
o Glucocorticoids (Cortisol)
o Adrenal Androgens
Adrenal Medulla:
o Catecholamine: Epinephrine and
norepinephrine (adrenaline and
noradrenaline)
PANCREAS
Glucagon (from α cells)
Insulin (from β cells)
Somatostatin (from δ cells)
OVARY
Estrogens
Progesterone
TESTIS
Testosterone
HORMONES BIOCHEMICAL REGULATORS (they can control lots of biological functions)
Can be classified based on how they act
hormones are secreted into the blood vessel, and carried to distant target cells, such as anterior Endocrine:
pituitary hormone ACTH, acts on adrenal (the BLOOD is the carrier to the rest of the body)
(they function in the nearby cells): hormones are secreted locally, and act on nearby cells, such as Paracrine
glucagon (from α cells) acts on pancreatic β cells
(they act on themselves): hormones are secreted locally, and act on the originating cells, such as Autocrine
1,25(OH)2vitD (can also function as endocrine and paracrine) from prostate and pancreas
hormones are secreted from neural axon terminals, such as Neuroendocrine and Neurotransmitter:
epinephrine and dopamine
CONTRL OF THE ENDOCRINE SYSTEM BY FEEDBACK AND RECEPTOR REGULATION
Feedback:
o Negative: e.g. hypothalamus-pituitary-thyroid axis
o Positive: e.g. at a particular point in the menstrual cycle, estrogen on LH surge (can also act in a positive
feedback manner it increase the release of the hormones) (The downstream hormones can go back to
the upstream endocrine glands to tell them when there is too much or too little it inhibits the pituitary
and the hypothalamus)
Receptor:
o Reversible reaction of hormones with their receptors, H + R HR
o Hormonal specific receptors (they only recognize their corresponding hormones)
o Tissue specific locations of receptors
o Down-regulation of receptors (when there is too much hormone then the receptors can be internalized)
Cell surface receptors and intracellular signaling pathway (they bind to the peptide hormones and pass on the
signal through signalling pathways)
o E.g. receptors for insulin, GH, PTH, TSH, LH (there are different types of receptors located in different
places)
o Rapid response (their response is very fast)
Intracellular receptors and gene regulation (they bind to the small molecules such as steroids and thyroid
hormones)
o Cytosolic or nuclear, function as hormone-regulated transcription factors, e.g. steroids, T4, 1,25(OH)2vitD
o Relatively slower response (slow mechanism they have to go through the transcription of genes)
HYPOTHALAMUS HORMONES:
The hypothalamus is the producer off some hormones and induces the anterior pituitary to release others (it
sends the signal to the pituitary via the portal system)
Releasing: TRH, CRH, GnRH, GHRH
Inhibiting: Dopamine & Somatostatin
HYPOTHALAMIC FACTORS REGULATE ANTERIOR PITUITARY FUNCTION
Hypothalamus
GnRH
CRH
GHRH
Somatostatin
(Inhibits the
release of both
of these)
TRH (has some
minor
stimulation on
the release of
the prolactin)
Dopamine
+ + + - + -
Anterior Pituitary
LH/FSH
GH
TSH
Prolactin
Targets
Gonads
Adrenal cortex
Liver & other
tissues
Thyroid
Breast & other
tissues
ENDOCRINE DISORDERS
Terminology:
o Hyper, hormone above normal level
o Eu, hormone within normal level
o Hypo, hormone below normal level
Examples:
o Oversecretion, e.g. gigantism where a pituitary adenoma overproduces growth hormone (in kids
tumors can induce the production of too much GH from the pituitary)
o Undersecretion, e.g. primary hypothyroidism (not enough release of the thyroid hormone)
o Failure of hormone responsiveness, e.g. Pseudohypoparathyroidism (if the receptor fails then
there can be low response they don’t have low levels of parathyroid hormone it is actually
high just the receptor levels are low and cannot respond)
o Abnormal hormone metabolism, e.g. 5α-reductase enzyme deficiency caused abnormal male
external genitalia development (biological genotype males appear as female; there is the
deficiency of the enzymes in the metabolic pathway and hence the final hormonal product
cannot be produced efficiently
VARIABLE CONCENTRATION OF HORMONE IN BLOOD
Androgens, Estrogens
(act on the gonads for the
production of these)
Cortisol
IGF-1
T4, T3
EPISODIC SECRETION:
- Up and down, up and down there is no
real pattern
STRESS RESPONSE:
- E.g. prolactin venipuncture can increase
this (they are scared of the needle)