HPA + Thyroidal axis

Question 1

Where does the thyroid gland develop from?

Answer 1

Pharyngeal pouches before migrating into the neck to its adult position

Question 2

Describe the thyroidal axis?

Answer 2

TRH - Hypothalamus
TSH - Anterior pituitary
T3/T4 - Thyroid gland

Question 3

How are T3 + T4 hormones produced?

Answer 3

Iodine is absorbed from the diet and converted to I-
I- is added to the tyrosine units of thyroglobin to form T3 or T4
T3= mostly and is more potent

Question 4

What is hypothyroidism, what are the types and what hormones are affected?

Answer 4

hypothyroidism = low levels of thyroid home 
Primary = defect in thyroid -> normal TSH + low T3/4
central = defect in pituitary/hypothalamus -> LOW EVERYTHING

Question 5

What are some symptoms of hypothyrodism?

How do we treat hypothyroidism?

Answer 5

dry skin
brittle nails 
menorhagia - heavy periods 
weight gain 
cold and fatigue 

Treated using levothyroxine = block and replace or dose titration

Question 6

What is thyrotoxicosis?

What are typical features?

Answer 6

Clinical syndrome when the tissues are exposed to very high levels of thyroid hormone

• weight loss but appetite
• missed/irregular periods
• lack of energy
• mood changes

Question 7

What is graves disease?

Answer 7

Auto immune disorder which is characterised by hyperthyroidism

Autoantibodies are produced which mimic thyroid stimulating hormone = TSH receptor antibodies

The autoantibodies can bind to thyroid stimulating receptors on the thyroid gland which causes the thyroid gland to synthesis more T3 + T4

This provides negative feedback on the hypothalamus and pituitary gland but the thyroid stimulating receptor is still active

There are other antibodies e.g thyroglobulin antibodies and thyroid peroxidase antibodies

Question 8

What are some typical features associated with hyper thyroidism and graves?

Answer 8

Thyroid eye disease: Swelling of extra occular muscles and lymphocytic infiltration
dermopathy : skin thickening due to accumulation of amino glycans and lymphocyte infiltration

Question 9

What can cause hyperthyroidism?

Answer 9

Toxic multi nodular goitre : Independent of the pituitary
Graves disease
Toxic adenoma : Only one area of thyroid produces XS hormones
TSHoma ( pituitary tumour)

Question 10

How do we investigate thyroid problems?

Answer 10

TSH auto antibodies - Graves
TPO antibodies = hasimotos
Ultrasounds indicate nodules

Question 11

How do we treat hyper thyroidism?

Answer 11

Propanolol - stop symptoms
Carbimazole
Radio active iodine: Iodine tagged with radioactive tracer and kills the thyroid follicular cells
Surgery

Question 12

What is a thyroid storm?

What are some signs + symptoms?

Answer 12

Major complication of hyper thyroidism
Life threatening event which is caused by an XS of thyroid hormones

Tachycardia, pyrexia, vomiting, cardiac failure, congestive hepatomegaly, respiratory distress

Question 13

What is thyroiditis?

What normally triggers it?

Answer 13

• Inflammation of the thyroid gland -> thyrotoxicosis -> hypothyroidism
  Triggered by auto immune diseases such De Quervain’s or Ridels

Question 14

What is the effect of amiodarone?

Answer 14

Drug that can cause severe hypo or hyperthyroidism

1: Increased thyroid hormones
2: Direct toxic effect causing leakage of contents out of the cell

Question 15

Describe the adrenal axis?

Answer 15

CRH: Hypothalamus
ACTH: Pituitary
Cortisol: Adrenal cortex ( zona fasiculata)

Question 16

What are the types of adrenal insufficiencies?

Answer 16

Primary = fault in adrenal gland 
Secondary = HPA axis fault. No mineralocorticoid receptor

Question 17

What is Addisons disease?

Answer 17

Addison’s disease = auto immune disease causing primary adrenal insufficiency - cortisol and aldosterone deficiencies
Symptoms = lack of energy or motivation,muscle weakness,low mood, loss of appetite and unintentional weight loss, increased thirst

Question 18

How do we diagnose and treat adrenal deficiencies?

Answer 18

9am cortisol measurements as dirunal variation
ACTH measurements - secondary adrenal insufficiencies

steroids : produces negative feedback on the pituitary to supress CRH + ACTH. Long term use may cause atrophy of the adrenal gland

Question 19

What are some of the functions of the hypothalamus ?

Answer 19

Homeostasis
Sleep
Weight and appetite 
Hormone synthesis 
HPA axis control

Question 20

Where does the APG develop from?

Where does the PPG develop from?

Answer 20

Rathkes pouch = protrouding ectodermal tissue from the roof of the mouth
Neuroectodermal tissue from the diencephalon

Question 21

What is Cushings disease + symptoms?

What is Cushings syndrome?

Answer 21

XS cortisol due to increased ACTH release from the pituitary 
Plethora
Hump back fat
thinning of the limbs 
hair loss 
abdominal obesity 
lethary 
low libido and erectile dysfunction 

Cushing syndrome = XS cortisol it may not be due to increased ACTH

Question 22

How do we diagnose Cushings?

How do we treat Cushings?

Answer 22

9am Cortisol - dirunal variation
ACTH measurements - cushings disease
Dexomethosone supression test: Dexomethosone would cause ACTH + cortisol to decrease, this would not happen in Cushings

• Drugs that inhibit steroidgenesis
• Removing the effector organs of cortisol e.g adrenakl glands

Question 23

What type of secretion is GnRH?
Describe the gonadol axis ?
How do we treat faults of this axis?

Answer 23

Pulsatile, is at low frequency before puberty and then will increase

• LH = increased frequency pulses
• FSH = low frequency pulses
• e.g increased frequency at ovulation

GnRH
LH/FSH
Oestrogen/progesterone/tesosterone
Hormonal replacement therapy will restore these faults. But exogenous testosterone in males will not restore their fertility.

Question 24

How is prolactin regulated?

What does high levels of pro lactin cause?

Answer 24

prolactin - lactation + enlargement of mammary glands

Regulated by inhibition via dopamine
Release of dopamine -> no prolactin
Less dopamine -> more prolactin
Dopamine inhibits pro lactin release

Inhibits GnRH release -> hypogonadism

Question 25

What are prolactinomas?

What are the 2 types of prolactinomas?

Answer 25

They are pituitary tumours which disrupt the inhibitor signals of dopamine leading to hyper prolactinaemia

Micro prolactinoma < 1CM (<2000 micrograms)
Macro prolactinoma> 1CM (>400 micrograms)

Question 26

What regulates HGH ?

How does HGH exhibit its effects?

Answer 26

Human growth hormone releasing hormone
Human growth hormone inhibiting hormone ( somatostatin)

IGF-1 - affects glucose metabolism
When glucose = high less growth hormone is released
High IGF-1 = less HGH

Question 27

What is acromegaly?
What are some common symptoms?
How do we diagnose acromegaly?

Answer 27

Disorder that occurs in adult hood when there is an XS of human growth hormone

• enlargement of bones in face, hands and feet
• sweating
• change in ring/shoe size
• lethargy

Diagnosis

• Measure IGF-1 + HGH
• Oral glucose tolerance test: High glucose will not cause HGH to decrease

Question 28

What is diabetes insipidus?

Answer 28

• Insufficient ADH
• Large volumes of dilute urine
• ## Use desmopressin to treat ( analogue of vasopressin/ADH)

Question 29

What is SIADH?

Answer 29

Syndrome of inappropriate ADH

• XS ADH produced
• Na+ loss in the urine
• Conc urine is produced

Question 30

What is pituitary apoplexy?

What is Sheehans syndrome?

Answer 30

Stalk compressed causing infarction

PPH causes infarction of the pituitary gland and it enlarges after birth