Biochemistry - Pituitary Function and Pituitary Disease

Question 1

Acidophi

Answer 1

Somatotrophs

Lactotrophs

Question 2

Basophils

Answer 2

Thyrotrophs
Corticotrophs
Gonadotrophs

Question 3

Chromophobe

Answer 3

Prolactin secretion

Question 4

Somatotrophs secrete

Answer 4

Growth Hormone (entire body)

Question 5

LActrotrophs secrete

Answer 5

Prolactin (mammary)

Question 6

Thyrotrophs secrete

Answer 6

TSH (thyroid)

Question 7

Corticotrophs secrete

Answer 7

ACTH (Adrenal)

Question 8

Gonadotrophs secrete

Answer 8

LH/FSH (Testes/Ovaries)

Question 9

Chromophobe secrete

Answer 9

(Prolactin)

Question 10

Corticotrophin releasing factor (CRF)

Answer 10

ACTH

Question 11

Thyrotrophin releasibg factor (TRH)

Answer 11

TSH

Question 12

Luteinising hormone RH (LHRH, GnRH)

Answer 12

LH/FSH

Question 13

Growth Hormon releasing hormone (GHRH)

Answer 13

GH

Question 14

Hypothalamic Peptide:

Releasing Factor

Answer 14

Corticotrophin releasing factor (CRF)
Thyrotrophin releasibg factor (TRH)
Luteinising hormone RH (LHRH, GnRH)
Growth Hormon releasing hormone (GHRH)

Question 15

Inhibiting Factor:

Answer 15

Somatostatin (GH RIF)

Dopamine (Prolactino RIF)

Question 16

Pituitary Tumours

Answer 16

Usually benign/slow growing (rarely metastesis)
Functional/Non-functional (non hormone secreting)
Local Effects
Secondary endocrine effects

Question 17

Hyper-function

Answer 17

Primary/Secondary (prolactinoma)
Usually single hormones involved
Prolactin, GH, ACTH

Question 18

Hypo-function

Answer 18

Usually generalised (al hormones effected)
Occasionally isolated (GH, LH/FSH, ACTH)
Causes: Tumours (primary/secondary). Infarction
Surgery/Irradiation, meningitis

Question 19

Basal Hormone measurements

Answer 19

• Pituitary hormones
• Target hormones

Limitations: diurinal changes

Question 20

Stimulation testing

Answer 20

Checking for deficiency

Individual/combined – give pituitary hormones/[physiological induce (fasting)
•	ACTH: hypoglycaemia. CRF
•	TSH: TRH
•	LH/FSH: LHRH
•	GH: Hypoglycaemia

Question 21

Suppression testing

Answer 21

Hormone Excess
ACTH: Dexamethasone (Blocks)
GH : Glucose

Question 22

Investigation of pituitary function:

Answer 22

Basal Hormone measurements

Stimulation testing
Suppression testing

Question 23

Growth Hormone Production – Induction

Answer 23

Stress
Exercise
Amino Acids
Sleep
Ghrelin

Question 24

Growth Hormone Production – Inhibition

Answer 24

Glucose/Somatisation

Question 25

Growth Hormone Production – Assessment of GH

Answer 25

IGF-1 | IGF-2 – shows excess production of GH

Question 26

Growth Hormone Production – Deficiency/Excess of GH

Answer 26

Deficiency – short stature | Excess – Gigantism acromegaly

Question 27

Growth Hormone Production – Metabolic effects of GH

Answer 27

Protein Biosynthesis – muscle, cartilage, viscerae Carbohydrate metabolism – insulin antagonism Lipid metabolism – Lipolysis Increased GIT absorption of calcium –(mainly by hydroxylation)

Question 28

Growth Hormone Production – Phenotypic Excess in GH Excess

Answer 28

Facial Changes Hands and feet enlarge Height increase in pre-pubertal

Question 29

Diagbosis

Answer 29

Biochemical Confirmation • Basal GH and IGF1 9not subject to pulsatile and diurnal and therefore wont effect drugs. • Suppression (GTT) • Other Anterior Pituitary function

Question 30

GH deficiency

Answer 30

Children:Short Stature Adults: Significantly less clear

Question 31

Destructive lesions

Answer 31

Tumours, surgery, irradiation, meningitis, head injury

Question 32

Functional: some forms of short stature

Answer 32

``` Pyschosocial, endocrine abnormalities, Laron dwarfism (GH receptor defect) – very rare ```

Question 33

Diagnosis

Answer 33

Inutero development is normal

Question 34

Diagnosis GH

Answer 34

Basal – GH/IGF-1 levels (Some overlap between normal and patho) Stimulation tests: • Insulin (Gold standard) – not pleasant for patient and dangerous • Glucagon (children <5 years) – stimulates GH production • Arginine +/- GHRH • Clonidine Failure of two stimuli required → GH +5 g/l

Question 35

Diagnostic response

Answer 35

1. Flat response – deficient | 2. Intermediate = some response

Question 36

Causes of Hyper-prolactinaemia

Answer 36

* Physiological | * Pathological

Question 37

Physiological

Answer 37

• Pregnancy • Stress • Drug induced: → Dopamnie receptor antagonist phenothiazines → Dopamine depleting agents methyl dopa → Oestrogens – oral contraceptives/PCOP • Macroprolactin – high molecular wt prolactin

Question 38

Macroprolactin diagnosis confirmation

Answer 38

Not Cleared therefor not responsive to treatment and so diagnostic

Question 39

Pathological causes

Answer 39

• Pituitary Tumour: 1. Prolactin secreting micro/macro adenoma 2. Acromegaly 3. Functionless pituitary tumour – affects of dopamine transfer • Lesions hypothalamic/pituitary stalk – lack of dopamine transfer • Primary hypothyroidism (TRH) – low thyroxine and so high TSH driven by TRH and so also stimulates Prolactin release • Chronic Renal Failure