Lecture 35: Thyroid Hormone / Parathyroid Hormone Flashcards Preview

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Flashcards in Lecture 35: Thyroid Hormone / Parathyroid Hormone Deck (25)

Prolactin Inhibitory Hormone (PIH) = ?

- Dopamine


Prolactin itself is involved in it's own ______ ______.

- Negative Feedback


Where is the thyroid gland?

- Just below the larynx


Thyroid gland structure:

- Small sacs/follicles
- Each follicle is surrounded by follicular cells


Follicular cells make _______ and secrete it into the follicle.

- Thyrogloubulin


Parafollicular cells make the hormone _____. It can sense how much _____ is in the blood.

- Calcitonin (reduces blood calcium levels)
- Calcium


Iodine reacts with ______. Iodised ___ moves into the follicular cells. Thyroid hormones are released from _____.

- Thyrogloubulin
- iodised TBG


Effects of thyroid hormone (general):

- Metabolic effects
- Growth (developmental) effects
- Via nuclear receptors that alter the transcription of genes.
- BMR (basal metabolic rate)


What is the Basal Metabolic Rate?

- Body's rate of energy expenditure under basal conditions (person is awake, at phyical and mental rest, lying down, no muscle movement, at a comfortable temperate and fasted 12-18h)


Effects of thyroid hormone (metabolic):

- Increased body heat production (inc oxygen consumption and ATP hydrolysis)
- Stimulate fat mobilisation and oxidation of fatty acids in many tissues. Decreased triglyceride and cholesterol levels.
- Stimulate carbohydrate metabolism, enhance insulin-dependent entry of glucose into cells
- Increase gluconeogenesis and glycogenolysis
- Increased proteolysis. Predominantly from muscle


Effects of thyroid hormone (growth):

- Growth retardation in thyroid deficiency
- Essential for development of fetal and neonatal brain (CNS)


What is Myxoedema?

- Not enough TH (Hyposecretion)
- Low metabolic rate
- Weight gain
- Cold intolerant
- Lethargic
- Slow heart rate


What is Graves Disease?

- Hypersecretion of TH
- High metabolic rate
- Weight Loss
- Heat intolerant
- Nervoisness
- Increased heart rate
- Tissue Swelling


What is Simple Goitre and how is it caused?

- Thyroid gland enlarges with continual stimulation by TSH (loss of negative feedback control as there is an inadequate concentration of iodine to make TH).


1% of calcium is in blood and tissues, in the plasma the reference range is...

- 9.2 - 10.4 mg/mL


Osteoblasts put ______ in the form of hydroaxyapatite back into the bone.

- Calcium


Osteoclasts absorb ______ and put it back into the blood stream.

- Calcium


The importance of Calcitonin:

- Need it to control calcium levels
- In children: osteoclasts liberate 5g of calcium every day


When calcium levels decrease. _______ is secreted.

- Parathyroid hormone


Parathyroid hormones increase....

- Osteoclast activity
- Break down bone to increase calcium levels in blood
- Reduce osteoblast activity
- Less bone deposition (prevention of hydroxyapatite formation)


Calcium regulation: PTH and Calcitonin:

- PTH and Calcitonin have opposite effects on blood calcium concentration
- Both act on bone (have receptors on bone cells) to bone breakdown (PTH) or bone formation (Calcitonin)
- NOT involved with hypothalamus


What happens when blood Ca2+ are low?

- Hypocalcemia:
Muscle tremors + spasms
Begins as plasma Ca2+ concentration falls to 6mg/dL
At 4mg/dL, larynx tightens, suffocation


What causes hypocalcemia?

- Diarrhea
- Vitamin D deficiency
- Thyroid tumors
- Underactive parathyroid glands
- Pregnancy


What effects does hypercalcemia have?

- Nerve and muscle tissue are less excitable


What is hyperparathyroidism?

- Soft bone
- Excess PTH secretion
- Raises the blood levels of calcium and phosphate ions
- Promotes formation of kidney stones composed of calcium

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