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Year 2 RE > Diagnostic Biochemistry of Endocrine Disorders > Flashcards

Diagnostic Biochemistry of Endocrine Disorders Flashcards

1
Q

What is the main biochemistry marker of choice to assess the thyroid gland?

1 - TSH
2 - T4
3 - T3
4 - TSH autoantibodies

A

1 - TSH

  • thyroid stimulating hormone
  • secreted by anterior pituitary gland
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2
Q

How much triiodothyronine (T3) and thyroxine (T4) are generally secreted daily?

A
  • T4 = 100mcg/day

- T3 = 6mcg/day

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3
Q

In a 50 year old female who is tired, lethargic, has night sweats and some weight loss, with the following thyroid blood biochemistry results:

TSH: <0.01 mU/L 0.3- 4.2
FT4: 32 pmol/L 12- 22
FT3: 9 pmol/L 3.1- 6.8

Does this patient have hypo or hyperthyroidism?

A
  • hyperthyroidism

- likely to be primary hyperthyroidism as TSH levels are low but still high T3 and T4

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4
Q

In hyperthyroidism, what happens to the functions of cells in the body?

A
  • all cells go into over activation
  • agitation, fine tremor, warm moist skin, palmar erythema
  • sinus tachycardia, atrial fibrillation, heart failure, peripheral oedema
  • muscle wasting, proximal myopathy, hyper-reflexia
  • splenomegaly (enlarged spleen), lymphadenopathy (enlarged lymph nodes)
  • gynaecomastia in men
  • extrathyroid manifestations ofGraves’ (rare): thyroid acropachy, thyroid dermopathy.
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5
Q

What are the 5 main causes of hyperthyroidism, and which of these is most common?

A

1 - thyroid enlargement (a goitre)
2 - graves’ disease (autoimmune disease) - MOST COMMON
3 - toxic multinodular goitre: non-tender thyroid nodules
4 - toxic adenoma: unilateral, non-tender thyroid mass
5 - subacute thyroiditis:tender, firm, irregular, diffuse/asymmetric enlargement
6 - amiodarone-inducedthyroiditis (cardiac medication): small goitre usually present

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6
Q

If a patient has hyperthyroidism and you suspect Graves disease, what is the main antibody that needs to be assessed?

A
  • thyroid stimulating hormone receptor antibody (TRaBs)
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7
Q

If a patient has hyperthyroidism and you suspect thyroiditis, what marker should be assessed?

A
  • Pentraxin C-reactive proteins (CRP) an inflammatory marker

- thyroiditis is an inflammatory condition

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8
Q

If a patient has hyperthyroidism and you suspect postpartum thyroiditis, what marker should be assessed?

A
  • TPOAbs (Thyroid peroxidase antibodies)

- thyroid peroxidase is used to create triiodothyronine (T3) and thyroxine (T4)

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9
Q

If a patient has hyperthyroidism which organ must be screened prior to starting any anti-thyroid medications?

A
  • liver

- full blood count is also required

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10
Q

If a patient has hyperthyroidism and you suspect there may be an enlargement of the neck or a nodule, what would be the first imaging modality used?

A
  • ultrasound
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11
Q

What is Euthyroid sick?

  • eu = good/normal
  • thyroid = thyroid gland
A
  • abnormal findings on thyroid function tests occurring without thyroidal illness (NTI), without preexisting hypothalamic-pituitary and thyroid gland dysfunction
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12
Q

Euthyroid sick is when there is an abnormal findings on thyroid function tests occurring without thyroidal illness (NTI), without preexisting hypothalamic-pituitary and thyroid gland dysfunction

  • eu = good/normal
  • thyroid = thyroid gland

What states does this normally occur in?

A
  • catabolic states (breakdown of larger molecules into smaller molecules for energy)
  • starvation or severe illness
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13
Q

Euthyroid sick is when there is an abnormal findings on thyroid function tests occurring without thyroidal illness (NTI), without preexisting hypothalamic-pituitary and thyroid gland dysfunction

  • eu = good/normal
  • thyroid = thyroid gland

This normally occur in catabolic states (breakdown of larger molecules into smaller molecules for energy), such as starvation or severe illness. The body essentially shuts down energy dependent functions that it decides are not essential. There is an enzyme in the thyroid that is down regulated in catabolic states, that may account for the abnormal thyroid function. What is this enzyme?

A
  • de-iodinase

- converts thyroxine (T4) into the active form of triiodothyronine (T3)

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14
Q

Should we measure thyroid function in a sick patient with suspected Sick Euthyroid?

A
  • no
  • thyroid hormone decreases, but then rebounds in Sick Euthyroid
  • it is difficult to determine what point they are at, so measurement of thyroid gland may be pointless
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15
Q

The adrenal gland is part of the hypothalamic pituitary adrenal axis. What does the hypothalamus and in turn the pituitary gland secrete to stimulate the adrenal glands?

A
  • hypothalamus secretes corticotropin-releasing hormone

- pituitary gland secretes adrenocorticotropic hormone

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16
Q

The adrenal gland has 2 main parts, the medulla and the cortex. What are main molecules that the medulla secretes?

A
  • catecholamines
    1 - adrenaline
    2 - noradrenaline
    3 - dopamine
17
Q

The adrenal gland has 2 main parts, the medulla and the cortex. The cortex can be further divided into 3 parts, label the image below using these labels:

zona reticularis
zona glomerulosa
zona fasciculata

A 
1 = zona glomerulosa (outermost layer)
2 = zona fasciculata (middle layer) 
3 = zona reticularis (innermost layer)
18
Q

The adrenal gland has 2 main parts, the medulla and the cortex. The cortex can be further divided into 3 parts, using GFR:

1 = zona glomerulosa (outermost layer)
2 = zona fasciculata (middle layer) 
3 = zona reticularis (innermost layer)

What does the phrase the deeper you get the sweeter it gets mean in relation to what the adrenal gland secretes?

A
  • zona glomerulosa (outermost layer) = salts (mineralocorticoids = Aldosterone)
  • zona fasciculata (middle layer) = sugar (Glucocorticoids = cortisol)
  • zona reticularis (innermost layer) = sex (Androgens = Dehydroepiandrosterone)
19
Q

The adrenal gland has 2 main parts, the medulla and the cortex. The cortex can be further divided into 3 parts, using GFR we can remember them, and see here examples of what each layer secretes:

  • zona glomerulosa (outermost layer) = salts (mineralocorticoids = Aldosterone)
  • zona fasciculata (middle layer) = sugar (Glucocorticoids = cortisol)
  • zona reticularis (innermost layer) = sex (Androgens = Dehydroepiandrosterone)

Why are mineralocorticoids, called mineralocorticoids?

A
  • mineral = as they are involved in maintenance of salts in the body (aldosterone)
  • corticoid = steroid
20
Q

The adrenal gland has 2 main parts, the medulla and the cortex. The cortex can be further divided into 3 parts, using GFR we can remember them, and see here examples of what each layer secretes:

  • zona glomerulosa (outermost layer) = salts (mineralocorticoids = Aldosterone)
  • zona fasciculata (middle layer) = sugar (Glucocorticoids = cortisol)
  • zona reticularis (innermost layer) = sex (Androgens = Dehydroepiandrosterone)

Why are glucocorticoids, called glucocorticoids?

A
  • gluc = glucose
  • corticoid = steroid
  • cortisol is an example
21
Q

The adrenal gland has 2 main parts, the medulla and the cortex. The cortex can be further divided into 3 parts, using GFR we can remember them, and see here examples of what each layer secretes:

  • zona glomerulosa (outermost layer) = salts (mineralocorticoids = Aldosterone)
  • zona fasciculata (middle layer) = sugar (Glucocorticoids = cortisol)
  • zona reticularis (innermost layer) = sex (Androgens = Dehydroepiandrosterone)

Why are androgens, called androgens?

A
  • andr = greek for man

- hormones involved in reproduction

22
Q

The adrenal gland has 2 main parts, the medulla and the cortex. The cortex can be further divided into 3 parts, using GFR we can remember them, and see here examples of what each layer secretes:

  • zona glomerulosa (outermost layer) = salts (mineralocorticoids = Aldosterone)
  • zona fasciculata (middle layer) = sugar (Glucocorticoids = cortisol)
  • zona reticularis (innermost layer) = sex (Androgens = Dehydroepiandrosterone)

What is Addisons disease also called adrenal insufficiency?

A
  • problem is in adrenal gland

- lack of cortisol and aldosterone

23
Q

Addisons disease, also called adrenal insufficiency is a problem is in adrenal gland, causing a lack of cortisol and aldosterone secretion. What is the most common cause of this?

1 - tumour
2 - autoimmune
3 - low cholesterol levels
4 - infection

A

2 - autoimmune disease

24
Q

What is secondary adrenal insufficiency?

A
  • a problem not in the adrenal gland
  • likely to be in the pituitary gland which releases adrenocorticotropic hormone (ACTH)
  • causing a lack of cortisol only as this is stimulated by ACTH
25
Q

What is cushings syndrome?

A
  • elevated levels of the glucocorticoid cortisol
26
Q

Cushings syndrome is elevated levels of the glucocorticoid cortisol. What are the 4 main things that can cause cushings syndrome and which is most common?

A 
1 - endogenous adrenal gland secretion
2 - adrenal tumour
3 - pituitary tumour = MOST COMMON
4 - ectopic tumour
5 - exogenous steroid medication
27
Q

In the kidneys, what hormone does cortisol mimic that will in-turn increase BP by retaining Na+ and H2O?

A
  • aldosterone
28
Q

In the kidneys, cortisol mimics aldosterone in distal convoluted tubules. What will this then cause in the kidneys?

A
  • increased Na+ and H2O re-absorption
  • hypertension, due to Na+ retention
  • K+ & H+ are lost and HCO3- is retained
  • metabolic hypokalaemic alkalosis (due to loss of H+ in urine and retention of HCO3-)
29
Q

Cushings syndrome is elevated levels of the glucocorticoid cortisol, this can be dependent or independent to Adrenocorticotropic hormone (ACTH). What is the difference between ACTH dependent and independent cushings?

A
  • ACTH dependent = ACTH is driving excessive secretion of cortisol
  • ACTH independent = ACTH is NOT driving excessive secretion of cortisol
30
Q

Cushings syndrome is elevated levels of the glucocorticoid cortisol, this can be dependent or independent to Adrenocorticotropic hormone (ACTH), explained below:

  • ACTH dependent = ACTH is driving excessive secretion of cortisol
  • ACTH independent = ACTH is NOT driving excessive secretion of cortisol

ACTH is the most common cause of cushings syndrome. What is the main cause of ACTH dependent cushings?

A

1st - pituitary adenoma

2nd - ectopic adenoma

31
Q

Cushings syndrome is elevated levels of the glucocorticoid cortisol, this can be dependent or independent to Adrenocorticotropic hormone (ACTH), explained below:

  • ACTH dependent = ACTH is driving excessive secretion of cortisol
  • ACTH independent = ACTH is NOT driving excessive secretion of cortisol

What are the 2 the main cause of ACTH independent cushings?

A
  • therapeutic corticosteroid administration

- adrenal tumour

32
Q

The adrenal gland is part of the hypothalamic pituitary adrenal (HPA) axis, where the following occurs to cause the secretion of cortisol:

  • hypothalamus secretes corticotropin-releasing hormone (CTH)
  • pituitary gland secretes adrenocorticotropic hormone (ACTH)

In instances where the adrenal cortex, specifically the zona fasciculata (middle layer secreting glucocorticoids such as cortisol) is impaired and does not respond to ACTH, which is called primary adrenal insufficiency, what then happens to the negative feedback loop of the HPA axis?

A
  • glucocorticoids (cortisol) does not provide inhibition to hypothalamus or pituitary gland
  • CTH and ACTH levels are increased
33
Q

The adrenal gland is part of the hypothalamic pituitary adrenal (HPA) axis, where the following occurs to cause the secretion of cortisol:

  • hypothalamus secretes corticotropin-releasing hormone (CTH)
  • pituitary gland secretes adrenocorticotropic hormone (ACTH)

In secondary adrenal insufficiency, what then happens to the negative feedback loop of the HPA axis if the hypothalamus is affected?

A
  • reduced CTH means low ACTH (pituitary gland) and low cortisol (adrenal) secreted
  • low cortisol will inhibit pituitary gland further meaning even less ACTH and less cortisol
34
Q

The adrenal gland is part of the hypothalamic pituitary adrenal (HPA) axis, where the following occurs to cause the secretion of cortisol:

  • hypothalamus secretes corticotropin-releasing hormone (CTH)
  • pituitary gland secretes adrenocorticotropic hormone (ACTH)

In secondary adrenal insufficiency, what then happens to the negative feedback loop of the HPA axis if the pituitary gland is affected?

A
  • pituitary gland does not respond to CTH released from the hypothalamus
  • pituitary gland secretes less ACTH and less cortisol is secreted from adrenal gland
  • lower levels of cortisol then inhibit hypothalamus and pituitary gland further
35
Q

What are the 3 main causes of primary adrenal insufficiency?

A

1 - autoimmune disease
2 - tuberculosis
3 - metastases

36
Q

What are the 2 main causes of secondary adrenal insufficiency?

A

1 - hypopituitarism

2 - isolated ACTH deficiency

37
Q

What are the 2 main causes of tertiary adrenal insufficiency?

A
  • chronic use of glucocorticoids
38
Q

To assess for adrenal insufficiency we can perform a short synacthen test. What is this test?

synacthen = ACTH analogue

A
  • patients cortisol levels are measured pre and post administration (normally after 60 minutes) of a synthetic adenocorticotrophic Hormone called synacthen

Year 2 RE (53 decks)

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