Measuring Hormones

1
Measuring Hormones

• Radioimmunoassay - hormone is labeled with
  radioactivity and combined with antibody for that
  hormone. Non-labeled hormone sample is added.
• Allows for the detection of hormones in minute
  concentrations and with a high degree of
  specificity.
• Increased accuracy of diagnosis of pathologies
  characterized by hormonal excess or deficiency.
• Research- greatly enhanced our understanding of
  how hormones work

2
Measuring Hormones

• Doctor runs blood panel, hormones measured by
  RIA.
• High pituitary hormones might suggest a pituitary
  adenoma
• High thyroid hormone can be an indicator of
  Graves disease
• body makes antibodies that actually bind and
  stimulate TSHR, stimulating thyroid hormone
  production
• Causes goiter (thyroid hyperplasia), wasting, and
  difficulty concentrating
• Low thyroid hormone hypothyroid
• Fertility problems, measure reproductive hormones

3
Displacement Curve
4
Measuring Hormone Receptors

• Research
• Many cancers are responsive to hormone.
• Hormone receptors are often quantified in breast
  cancer biopsies.
• Receptor positive
• Receptor negative
• Important because progesterone and estrogen, not
  only regulate normal breast development, but also
  breast cancer progression.
• Progesterone and estrogen can stimulate breast
  cancer cell proliferation
• These cancers often respond to treatment with
  progesterone or estrogen antagonists (ex.
  Tamoxifen)

5
Hormone-Receptor Interaction

• Kd - dissociation constant - equilibrium constant
  the measures the likelihood of a complex
  (hormone-receptor) to separate reversibly into
  smaller components
• Inverse of affinity constant (Ka)
• Same as in biochemistry
• Receptors bind specific hormones with very high
  affinity (Kd 10-8 to 10-12 M)
• This means that at 10-8 M of hormone, half of the
  receptors for that hormone will be bound.
• Hormones also have a particular Kd for their
  binding proteins

Kd H R HR
Ka HR HR
6
RAI vs. Scatchard Plot

• Both
• Use radioactively labeled hormone

• RIA
• Measures hormone
• Involves hormone binding to antibody

• Scatchard Plot
• Measures receptors
• Involves hormone binding to receptors

7
PHSL 410 - Endocrine

• Lecture 3
• Neuroendocrinology
• Posterior Pituitary

8
The Pituitary Gland is Made up of 3 Lobes
optic chiasm
Hypothalamus
hypothalamus
pituitary gland

• Maintain homeostasis
• Growth Control
• Fertility
• Lactation
• Stress management

IL
AL
PL
http//www.vivo.colostate.edu/hbooks/pathphys/endo
crine/hypopit/sagpitbig.jpg
9

• Anterior pituitary (adenohypophysis)
• Secretes peptide hormones ACTH, GH, THS, FSH,
  LH, PRL.
• Stimulated by releasing hormones from
  hypothalamus
• Small-diameter neurons, cell bodies in
  hypothalamus, synapse at portal veins and secrete
  releasing hormones
• Posteroir pituitary (neurophypophysis)
• Secretes arginine vasopressin (ADH) and
  oxcytocin.
• Large-diameter neurons, cell bodies in
  hypothalamus, synapse in posterior pituitary

10
Control of Multiple Endocrine Organs

• The hypothalamus and pituitary control a number
  of endocrine organs.
• The pituitary bridges and integrates neural and
  endocrine systems.
• Pituitary portal system - carries neuropeptides
  (releasing hormones) from hypothalamus and
  pituitary stalk to the anterior pituitary.

11
Pituitary hormone production
Somatotropes
Lactotropes
Corticotropes
Gonadotropes
Thyrotropes
FSHb
Prl
GH
TSHb
POMC
LHb
Growth Hormone
Follicle Stimulating LuteinizingHormones
Thyroid Stimulating Hormone
Prolactin
ACTH
Liver and other organs
Adrenal Gland
Thyroid
Mammary Glands
Gonads
12
Releasing Hormones

• Produced from small-diameter neurons in
  hypothalamus
• Control secretion of peptide hormones from
  anterior pituitary (GH, TSH, ACTH, LH, FSH, PRL).
• Are discharged into median eminence and neural
  stalk where they enter pituitary portal veins and
  are taken to anterior pituitary.

13
Pituitary Portal System

• A portal system is a system that begins and ends
  in capillaries
• Pituitary Portal System supplies blood to the
  anterior lobe of the pituitary.
• Hormones travel from capillaries of median
  eminence through veins to capillaries of anterior
  lobe (2 capillary beds).
• Results in a significant reduction in the
  necessary production of hypothalamic releasing
  hormones.

14
Hypothalamic-pituitary-gonadal Axis
Hypothalamus
GnRH (releasing hormone)
Pituitary -gonadotrope cells
LH/FSH
Gonad
Sex Steroids
15
Hypothalamic-pituitary-adrenal Axis
Hypothalamus
CRH (releasing hormone)
Pituitary -corticotrope cells
ACTH
Adrenal gland
Cortisol
16
Hypothalamic and Anterior Pituitary Hormones
17
Hypothalamic and Posterior Pituitary Hormones
18
Pituitary organogenesis
P Posterior, I Intermediate, A Anterior
19
Pituitary diseasessignificance of studying
pituitary

• Hormone deficiency
• 1/4000 births
• IGHD GH
• CPHD transcription factor defects
• syndromic CPHD involves head development treatm
  ent hormone replacement
• Pituitary adenomas
• commonly found at autopsy
• 30 detected tumors invasive, 1 metastatic
• genetics not well understood
• treatment surgery, drugs

20
How many transcription factors does it take to
build a pituitary gland?
Pitx1,2
ACTH
GH
Lhx3,4
Tpit
NeuroD
Rpx
Prop1
Pit1
PRL
Foxl2 (forkhead)
Sf1
TSH
LH/FSH
21
Test Question

• Bromocriptine, a dopamine (DA) receptor agonist
  (it act like DA on the DA receptor), is often
  used to treat hyperprolactinemia. What is its
  most likely mechanism of action based on your
  knowledge of the hypothalamic-pituitary axis
• a. stimulation of the release of a hypothalamic
  prolactin inhibiting factor
• b. inhibition of the release of a hypothalamic
  prolactin stimulating factor
• c. a direct inhibitory action on pituitary
  lactotrophs (prolactin secreting cells)

22
Bromocriptine, a dopamine (DA) receptor agonist
(it act like DA on the DA receptor), is often
used to treat hyperprolactinemia. What is its
most likely mechanism of action based on your
knowledge of the hypothalamic-pituitary axis?

• a. stimulation of the release of a hypothalamic
  prolactin inhibiting factor

Name a hypothalamic prolactin inhibiting factor.
Where are dopamine receptors located?
23
Bromocriptine, a dopamine (DA) receptor agonist
(it act like DA on the DA receptor), is often
used to treat hyperprolactinemia. What is its
most likely mechanism of action based on your
knowledge of the hypothalamic-pituitary axis?

• a. stimulation of the release of a hypothalamic
  prolactin inhibiting factor

24
Bromocriptine, a dopamine (DA) receptor agonist
(it act like DA on the DA receptor), is often
used to treat hyperprolactinemia. What is its
most likely mechanism of action based on your
knowledge of the hypothalamic-pituitary axis?

• b. inhibition of the release of a hypothalamic
  prolactin stimulating factor

Is there a hypothalamic prolactin stimulating
factor?
25
Bromocriptine, a dopamine (DA) receptor agonist
(it act like DA on the DA receptor), is often
used to treat hyperprolactinemia. What is its
most likely mechanism of action based on your
knowledge of the hypothalamic-pituitary axis?

• b. inhibition of the release of a hypothalamic
  prolactin stimulating factor

26
Bromocriptine, a dopamine (DA) receptor agonist
(it act like DA on the DA receptor), is often
used to treat hyperprolactinemia. What is its
most likely mechanism of action based on your
knowledge of the hypothalamic-pituitary axis?

• c. a direct inhibitory action on pituitary
  lactotrophs (prolactin secreting cells)