Disorders of the thyroid gland Flashcards
How many lobes does the pituitary gland have?
two lobes
Where does the pituitary gland lie?
lies below the brain in the Sella Turcica
What is the anterior lobe of the pituitary gland derived from?
The anterior lobe (adenohypophysis) is derived from an invagination of the roof of the embryonic oropharynx
- Known as Rathke’s pouch.
What forms the pituitary stalk and what does it connect?
A notochordal projection forms the pituitary stalk
- Connects the gland to the brain and also the posterior lobe of the pituitary (neurohypophysis).
Describe the blood supply of the pituitary gland?
The pituitary gland has a dual blood supply.
- The first is via the long and short pituitary arteries
- The second is from the hypophyseal portal circulation.
This begins as a capillary plexus around the Arcuate nucleus of hypo to anterior
How were pituitary cell types orignally characterised?
classified by their staining characteristics with acidic (orange-G) and basic (aldehyde fuscin) dyes
Function of Prolactin
Breast milk production
- prolactin is an anterior pituitary hormone
Function of ADH
Water regulation
Function of oxytocin
Breast milk expansion
State the single word nomenclature for the following:
- LH/FSH
- GH
- TSH
- ACTH
Respectively:
Gonadotrophin
Somatotrophin
Thyrotrophin
Corticotrophin
Draw or describe the general feedback loop of the hypothalamic
- pituitary axis?
Hypo.= Tertiary
(Anterior) Pituitary = secondary
End organ = Primary
-ve feedback is induced by end organ hormones
State the 3 major clinical presentations of pituitary tumours?
- Hormone hypersecretion
- Space occupying lesion (tumours present in skull or cranial)
- Headaches
- Visual loss (field defect)
- Cavernous Sinus Invasion - Hormone deficiency states
- Interference with surrounding normal pituitary
State the syndrome of excess GH
Acromegaly
State the syndrome of excess ACTH
Cushing’s disease
State the syndrome of excess TSH
Secondary thyrotoxicosis
State the syndrome of excess LH/FSH
Non-functioning pituitary tumour
State the syndrome of excess PROLACTIN
Prolactinoma
Draw or describe the GH feedback loop of the hypothalamic
- pituitary axis?
Blue is inhibitory effect (somatostatin)
red is stimulatory effect (GHRH)
IGF-1 stimulates chondrocytes for bone growth,
but also induces -ve feedback (GH also does this too)
State the systemic effects of GH/IGF-1 excess?
- Acral enlargement
- spade like hands rings too small
- Inc shoe size
- macroglossia
- carpal tunnel syndrome - Increased skin thickness
- Increased sweating
- Skin tags and acanthosis nigricans
- Change appearance
- inter-dental spacing
- Visceral enlargement
- Metabolic Changes
- Impaired fasting glucose
- Impaired glucose tolerance
- Diabetes mellitus
- Insulin resistance
- Reduced total cholesterol
- Increased triglycerides
- Increased nitrogen retention
State 8 consequences of GH/IGF-1 excess?
Cardiomyopathy
Hypertension
Bowel Polyps
Colonic Cancer
Multinodular goiter
Hypogonadism
Arthropathy
OSA
State 6 major actions of cortisol?
Proteins are catabolised
- Releases Amino Acids
Na+ and H2O Retention
- Maintains BP
Anti inflammatory
Increased gastric acid production
Increases plasma glucose levels
Increases lipolysis
- Provides energy
State how processes are affected by cortisol so it can increase plasma
glucose levels
- Inc gluconeogenesis
- Dec glucose utilisation
- Increases glycogenesis
- Inc glycogen storage
State the 3 major changes that occur from cushing’s syndrome?
Changes in protein and fat metabolism
Changes in sex hormones
Salt and water retention
Describe the effect as a result of change in protein and fat metabolism
from cushing’s syndrome?
Change in body shape
Central obesity
Moon face
Buffalo hump
Thin skin, easy bruising
Osteoporosis (brittle bones
Diabetes
Describe the effect as a result of change in sex hormones
from cushing’s syndrome?
Excess hair growth
Irregular periods
Problems conceiving
Impotence
Describe the effect as a result of salt and water retention
from cushing’s syndrome?
High blood pressure
Fluid retention
Describe how prolactin has a different feedback to all the other anterior
pituitary hormones?
Tonic release of Dopamine inhibits PRL release
- Works via a positive feedback mechanism
State the 3 drugs which can interfere with dopamine and prolactin
secretion?
Antiemetics
Antipsychotics
OCP/HRT
State 6 features of PRL excess (prolactinomas)
- Infertility
- Oligoamenorrhoea
- Amenorrhoea
- Galactorrhoea
- Reduced libido
- Impotence
How does excess PRL cause hypogonadism?
In hyperprolactinemia, which induces hypogonadism, the excess prolactin interferes with secretion of gonadotropin-releasing hormone
- Results in decreased testosterone/oestrogen
State the treatment for prolactinomas?
Dopamine agonists:
- bromocriptine,
- cabergoline
(not surgery)
Describe features of non-functioning pituitary tumour?
30% of all pituitary tumours
No syndrome of hormone excess produced
Cause symptoms due to space occupation
State 5 symptoms of non-functioning pituitary tumours?
- headache
- visual field defects
- nerve palsies
- interfere with rest of pituitary function
- deficiency of hormones
State the treatment for non-functioning pituitary tumours
surgery (transsphenoidal approach) ± radiotherapy
no effective medical therapy
State the effect of the loss of pituitary function with expanding tumour?
LH FSH
GH
TSH
ACTH
Prolactin
Respectivrly:
Sex
Growth
Metabolism
Survival
Stalk compression
Further down is increasing in biological importance
Describe the treatment for pituitary adenoma?
Surgery
Transsphenoidal
(Adrenalectomy - Nelson’s syndrome)
Radiotherapy
Slow
Drugs
Block hormone production
Stop Hormone Release
State 5 causes of pituitary failure?
Tumour
- Benign
- (Malignant)
Trauma
Infection
Inflammation
- Sarcoidosis
- Histiocytosis
iatrogenic
What is the effect of hypopituitarism on TH?
Bradycardia
Weight gain
Cold intolerance
Hypothermia
Constipation
What is the effect of hypopituitarism on sex steroids?
Oligomenorrhoea
Reduced libido
Hot flushes
Reduced body hair
What is the effect of hypopituitarism on reduced cortisol?
Tiredness
Weakness
Anorexia
Postural hypotension
Myalgia
What is the effect of hypopituitarism on reduced GH?
Tired
Central weight gain
State the treatment of hypopituitarism of:
- Thyroid
- Sex steroids
- Reduced cortisol
- Reduced GH
Thyroid
- Thyroxine
Sex Steroids
- Testosterone
- Oestrogen
Reduced Cortisol
- Hydrocortisone
Reduced GH
- Growth hormone
State the control of vasopressin?
Increased plasma osmolality
Decreased blood pressure (Baroreceptors)
Decreased PaO2 and increased PaCO2
- cortisol
- sex steroids
- angiotensin II
State the action of vasopressin?
Collecting ducts
increased permeability for H2O
reabsorbtion of free water
Vasoconstriction
State effects for Syndrome of Inappropriate ADH (SIADH)
Too much ADH
Brain injury/infection
Lung cancer/infection asthma IPPV
Metabolic
- Hypothyroidism
- Addison’s
State the diagnosis markers for SIADH?
Plasma Na+
(<130mmol/l)
Plasma osmolality
(>285mOsm/kg)
Urine osmolality
(>100mOsm/kg)
Urine Sodium
(>30mmol/l)
State treatment for SIADH?
Fluid restriction Demeclocyline ADH Antagonist (Tolvaptan)
How is diabetes inspidus caused by?
Underproduction ADH
Cranial:
Lack of Production
Nephrogenic:
Receptor resistance
State the diagnosis for diabetes inspidus?
Essentially too much urine being released
Polyuria (>3l)
OR
Polydipsia (excessive thirst)
Plasma Na+
Dec. Plasma osmolality (> 295 mosmol/kg)
Inc. Urine osmolality (< 700 mosmol/kg)
Inc. Urine Na+
What is the water deprivation test used for?
Used to differentiate between primary polydipsia (excessive or anormal thirst) and diabates insipidus (CDI/NDI) due to increased water output
C= Central N= Nephrogenic
