Hormones, Receptors & Assays TG

Question 1

Name the 5 specific classes of Hormones

Answer 1

1. Amino acid derivatives (dopamine, catecholamines, thyroid hormones)
2. Small neuropeptides (GnRH, TRH, somatostatin, vasopressin)
3. Large proteins (e.g. PTH, insulin, GH)
4. Steroid hormones (e.g. cortisol, oestrogen)
5. Vitamin derivatives (retinoids, Vitamin D)

Question 2

What are the functions of hormones?

Answer 2

Growth and development
Reproduction
Homeostasis (fluid and electrolyte balance, BP, heart rate, acid/base balance)
Energy production, utilisation and storage

Question 3

Describe Insulin–Receptor Interaction

Answer 3

Propogates a whole series of signals -> via activation of PI3 kinase- mobilizes GLUT4, translocates to the surface and allows glucose uptake

Question 4

SDescribe Steroid hormone/receptor interaction

Answer 4

Homodimer steroid receptors
Heterodimer recetors
Orphan receptors

Question 5

Explain the tropic/target hormone interaction

Answer 5

CNS inputs -> hypothalamus (Tear 1)–>
Pituitary (teir II) : paracrine cytokines and growht factors –>
Target gland (teir 3, peripheral hormones.

Question 6

What are the principles of Endocrine investigations?

Answer 6

Endocrine disease:

• hormone over production
• hormone underproduction
• hormone resistance

Paired measurement of target and trophic hormones

Question 7

Bioassays

Answer 7

Test a hormones FUNCTION

Question 8

Immunoassays- what are the problems?

Answer 8

Use competitive binding with a labelled antigen to find the bound hormone that they want

Hook effect - If you have a really high conc of hormone, it can artificially lower the signal as it swamps the antibody * don’t need to know more than that.

Cross reactivity
Heterophilic antibodies- Up to 20% of samples- can test for this by neutralizing the antibodies

Clinical context- Specificity of antibody

Question 9

Explain the High Dose Hook Effect

Answer 9

Usually affects tumour marker measurements: eg. AFP, Ferritin, CA-125, HCG, PSA, Prolactin, ACTH, hGH, Insulin

Question 10

What are heterophile antibodies

Answer 10

Antibodies that bind to animal IgG’s used in the reagent Ab (Ab is of low affinity)
Artifactually alters the signal strength
Commonly yields false positive reports, false negative results are also reported.
Up to 22% of assays are subject to interference.
How do you resolve this?

Overcome heterophile ab interference by: incubating test sample with excess IgG, and neutralising out heterophile antibodies

Question 11

To rule IN graves disease, what antibody would you screen for?

Answer 11

TRAB

- TSH receptor antibodies