Endocrine tactical problem-solving

Question 1

Overview of too much hormone

Answer 1

• Overactivity= excessive growth (gigantism)
• Diagnose by high plasma hormone levels and perturbed feedback
• Treat by blocking hormone synthesis or action (using drugs) removing the source (surgery)

Question 2

Overview of too little hormone

Answer 2

• Underactivity= restricted growth (dwarfism)
• Diagnose by low plasma hormone levels and perturbed feedback
• Treat by hormone replacement (restoration of normal levels)

Question 3

What does chronically fatigued and no energy suggest?

Answer 3

• Post-menopausal
• Age-related slow-down
• Metabolism
• Diabetes

Question 4

What does frequent headaches suggest?

Answer 4

• Post-menopausal
• Migraine
• Vascular inflammation
• Intracranial pressure
• Tumour

Question 5

What does low free T4 mean?

Answer 5

-Under-secretion of T4 from the thyroid and weight gain
-Possible thyroid gland failure and primary hypothyroidism
=TSH should be high in low T4 (if not- pituitary?)
=TPO antibodies (positive= primary autoimmune, negative= secondary)

Question 6

What could affect low fasting blood glucose?

Answer 6

• Thyroid problem lowering metabolic rate
• Insulin
• Cortisol

Question 7

What does borderline low plasma Na and K suggest?

Answer 7

-Problem with water balance
-Aldosterone
-AVP
-Cortisol
=Dilutional hyponatraemia

Question 8

What happens when LH and FSH levels are abnormally low after menopause?

Answer 8

-Unopposed peri and post menopausal gonadotrophins should be high
=due to lack of oestrogen and progesterone feedback from ovary
=suggests failure in pituitary gonadotrophin secretion

Question 9

Why is simple TE replacement for secondary hypothyroidism dangerous?

Answer 9

-T4 replacement exacerbates cortisol deficiency by:
=speeding up metabolism, thus more demand for glucose
=speeding up degradation of cortisol in the liver, reducing ability to make glucose in response to stress
=treating hypothyroidism without recognising concomitant hypoadrenalism may precipitate an Addisonian crisis

Question 10

How do you distinguish between primary and secondary adrenal failure?

Answer 10

-1º due to adrenocortical insufficiency (ZG, ZF & ZR affected)
-2º due to failure of pituitary ACTH secretion (ZF & ZR only affected)
=Short Synacthen test
=measure plasma cortisol

Question 11

What suggests pituitary failure in ACTH?

Answer 11

-9 o’clock resting plasma ACTH
=normally high in morning
=low-normal suggests failure in pituitary ACTH secretion

Question 12

How does skin appearance reflect hormone failure?

Answer 12

• T4 deficiency = dry skin, lowered metabolic rate
• sex steroid deficiency = soft, thin wrinkled skin;
• GH deficiency = soft, thin wrinkled skin;
• ACTH deficiency = pale skin

Question 13

In hypopituitarism, why does the repeat Synacthen test show increased ACTH?

Answer 13

• Initial ACTH treatment has caused adrenal ZF cell proliferation
• Adrenals have responded to second ACTH challenge

Question 14

What can be added to thyroxine treatment to correct low plasma sodium?

Answer 14

Cortisol

=relieves symptoms

Question 15

What does loss of cortisol feedback lead to?

Answer 15

-Reduces tonic vagal and glossopharyngeal inhibition of AVP release from posterior pituitary
=excessive AVP secretion leads to water uptake via kidney aquaporin channels, volume expansion and dilution of plasma biochemicals

Question 16

What is hypertension and low K normally consistent with?

Answer 16

-Excess mineralocorticoid activity at MR
=elevated aldosterone activating MR
=elevated cortisol or some other steroid activating MR

Question 17

What does low cortisone levels suggest?

Answer 17

-Problem with 11betaHSD2?
=low conversion of active cortisol to inactive cortisone
=suggests local cortisol action at kidney MR

Question 18

What defect is there in syndrome of apparent mineralocorticoid excess?

Answer 18

Mutation in HSD11B2 gene

Question 19

What does too much liquorice cause?

Answer 19

Inhibition of 11bHSD2