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KIN 131 > Endocrine Glands, Hormones and their Functions > Flashcards

Endocrine Glands, Hormones and their Functions Flashcards

1
Q

What is found in The Thyroid Gland?

A
  • Follicles – a ring of follicular epithelial cells that contain protein-rich colloid
  • Epithelial cells (simple cuboidal) are important for synthesis and secretion of thyroid hormones
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2
Q

What are Thyroid Hormones?

A
  • The thyroid gland produces thyroxine (T4) and triiodothyronine (T3)
  • Contain iodine (T3 has 3, T4 has 4)
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3
Q

Differentiate between T3 and T4:

A
  • [Plasma] of T4 > T3
  • Most of T4 is converted to T3 by deiodinases in the tissues – because of this T3 is considered the major thyroid hormone
  • T4 has a lower clearance rate, however, ∴ is the most common pharmacological prescribed to people with low levels of thyroid hormone
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4
Q

What are deiodinases?

A

Deiodinases are a family of enzymes that play a key role in the regulation of thyroid hormone activity by controlling the conversion of thyroxine (T4) to triiodothyronine (T3) and the removal of iodine from thyroid hormones. There are three main types of deiodinases: type 1 (D1), type 2 (D2), and type 3 (D3).

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5
Q

How is the thyroid gland controlled?

A
  • TRH -> TSH -> T3 and T4 production
  • TSH stimulates protein synthesis and turnover of organelles in follicular cells
  • Over-exposure of the thyroid gland to TSH causes hypertrophy of the follicular cells
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6
Q

What is the negative feedback in thyroid hormones secretion?

A
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7
Q

What are the Actions of Thyroid Hormones?

A
  • Receptors (found in the nuclei) for thyroid hormones are present on many effector cells and therefore have widespread effects (compared to other hormones that are more specific)
  • Receptors are found intracellularly, in the nucleus
  • T3 increases gene transcription and protein synthesis in its target cells
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8
Q

Explain

A
  1. T4 is bound to protein carrier in blood
  2. T4 diffuses across the cell membrane
  3. T4 is converted to T3 by deiodinases
  4. T3 binds to its receptor in nucles and impacts gene expression
  5. Altered gene expression alters protein expression and activity
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9
Q

Actions of Thyroid Hormone

How do thyroid hormones function in metabolism?

acts on pretty much every cell in the body

A

Metabolism

  • T3 increases carbohydrate absorption from the small intestines and increases fatty acid release from adipocytes
  • These actions provide energy that help maintain metabolism at a high rate

more thyroid hormones = more breakdon of nutrients and ATP syntheis

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10
Q

Actions of Thyroid Hormone

How do thyroid hormones affect beta-adrenergic receptors?

A

Upregulates beta-adrenergic receptors (targets of the catecholamines) in the heart and nervous system

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11
Q

Actions of Thyroid Hormone

[catecholamine] in the plasma is normal, but an individual is experiencing anxiousness, nervousness and a racing heart. Explain how the thyroid gland and tyroid hormones may play a role in these symtoms. How might this be treated?

A

you have a high level of thyroid hormones which cause there to be more receptors making it easier for catelcholines to bind and activate. Need to block beta-adrenergic receptors.

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12
Q

Actions of Thyroid Hormone

How do thyroid hormones affect growth and development?

A

Growth and Development

  • T3 required for the normal production of growth hormone in the anterior pituitary gland
  • Integral for neonatal development
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13
Q

Actions of Thyroid Hormone

What is neonatal development?

A
  • Formation of axon terminals, production of synapses, growth of dendrites and formation of myelin
  • Absence leads to syndrome called congenital hypothyroidism which leads to severely compromised intellectual functioning
  • Treated with exogenous T4
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14
Q

q

A

Most common cause of congenital hypothyroidism is poor development of thyroid gland
caused by iodine deficiency in the diet of the mother
* Prevented by iodized salt in most areas of the world (a small fraction of NaCl (table salt) is
replaced with NaI)

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15
Q

What is Hypothyroidism?

A
  • Chronically low levels of thyroid hormones in the blood
  • Typically, due to damage or loss of functional thyroid tissue or inadequate iodine consumption
  • Reduce [plasma] cancels the negative feedback control

need high conc to regulate negative feedback loop
anterior pituitary will continue to release

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16
Q

Hypothyroidism

What is Goiters?

A
  • Without the negative feedback look, the hypothalamus continues to release TRH and the anterior pituitary releases TSH but there is no effect on thyroid hormone
  • Overstimulating the thyroid gland can produce goiters

enlarged thyroid hormones

17
Q

What causes Hypothyroidism?

A

Autoimmune Thyroiditis:
autoimmune disruption of normal functioning of the thyroid gland

  • Hashimoto’s Disease: immune cells attack the cells of the thyroid gland
  • Treatable with pills containing T4

Secondary Hypothyroidism:
chronically reduced TSH release from anterior pituitary, lack of stimulation on the thyroid gland can cause atrophy

18
Q

What are Symptoms of Hypothyroidism?

A
  • Increased cold sensitivity and weight gain
  • ^^ both are due to reduced calorigenic actions normally stimulated by thyroid hormone
  • Lots of other non-specific effects i.e., changes in skin tone, gastrointestinal issues, fatigue etc.

byproduct of metabolim is heat so makes sense

19
Q

What is Hyperthyroidism (Thyrotoxosis)?

A

Chronically high levels of thyroid hormones in the blood

20
Q

Hyperthyroidism

What is Graves’ Disease?

A

Graves’ disease

  • Autoimmune disease
  • Production of antibodies that bind and activate TSH receptors on the thyroid gland leading to overstimulation of the thyroid gland
21
Q

What are Symptoms of Hyperthyroidism?

A
  • Heat intolerance, weight loss, increased appetite
  • Increased sympathetic nervous system activity (anxiety,
    tremors, jumpiness, increased heart rate)
22
Q

How are Symptoms of Hyperthyroidism treated?

A

Treated by:

  • Drugs that inhibit thyroid hormone synthesis
  • Surgically removing part of the thyroid gland or damaging the gland with radioactive iodine

ingest radioactive iodine specifically damages thyroid gland

23
Q

What is the Parathyroid Gland?
What stimulates it?

A
  • Parathyroid glands produce parathyroid hormones (PTH)
  • Ca2+ acts directly on secretory cells on the parathyroid gland
  • Decreased [Ca2+] stimulates PTH secretion and vice versa
24
Q

explain pathway

A

KIN 131 (44 decks)

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