Issues with Endocrine Function Flashcards
(15 cards)
Hormones
molecules (such as steroids, amino acid derivatives, polypeptides or proteins), which interact with receptors on their target cells, triggering biochemical reactions that modify the activity of the cell.
THE HYPOTHALAMUS
- Located in the brain
- Produces hormones that act on the pituitary gland
- Hypothalamic hormones stimulate or inhibit the release of pituitary hormones
THE PITUITARY GLAND
- Located in the brain
- Some pituitary hormones act on other glands located in various parts of the body (such as adrenal glands, thyroid, testes and ovaries), which in turn release their own hormones
- Other pituitary hormones directly affect their target organs
GENERAL HYPOTHALAMIC - PITUITARY - TARGET GLAND FUNCTION
Stimulation of receptors on the target cell triggers biochemical reactions that modify the activity of the cell
Negative feedback mechanisms control endocrine system activity.
The hormones released from the target gland feedback to the pituitary and/or hypothalamus, repressing further hormone release and thereby downregulating the system
NORMAL HORMONE FUNCTION
The normal functioning of hormones in the body is influenced by:
* Nutrition and absorption of nutrients necessary for hormone production
* Transportation of hormones by blood, lymph, and digestion
* Sensitivity of receptors that hormone is targeting
* Auto-immune targeting of a particular component in the hormone system, resulting in under or over production
* tumour growth of hormone- secreting cells
* destruction of hormone-secreting cells by an adjacent tumour or other pathological process
THE THYROID GLAND
- Iodine is bound to thyroglobulin by the enzyme thyroid peroxidase to form T4 and T3, which are then are released into the peripheral circulation.
- T3 can also be formed by conversion of T4 to T3
- The majority of thyroid hormones in the circulation are inactive (bound to binding globulins)
- Free T3 is more biologically active than free T4
PRIMARY HYPOTHYROIDISM - HASHIMOTO’S DISEASE (CHRONIC LYMPHOCYTIC THYROIDITIS)
- Most common cause of hypothyroidism in iodine sufficient countries
- Autoimmune disease associated with lymphocytic infiltration of the thyroid gland
- Destruction of thyroid cells by anti-thyroperoxidase (anti-TPO) antibodies
- In the early stages , T4 & T3 may be released into the circulation due to cell damage, causing transient hyperthyroidism * Ultimately, autoimmune destruction of the thyroid gland results in insufficient production of thyroid hormones
- Wide range of effects due to deficiency of thyroid hormone, resulting derangements in metabolic processes, & myxedematous infiltration
POSTPARTUM THYROIDITIS
- Lymphocytic thyroiditis affects up to 10% of postpartum women (and up to 25% of post-partum women with type 1 diabetes mellitus) up to 12 months after delivery.
- Frequently transient , resolving within 12 months
- Increased risk for recurrence of postpartum thyroiditis with future pregnancies or permanent hypothyroidism.
EUTHYROID SICK SYNDROME
- May be due to any severe, acute illness.
- Free T3 is reduced, but TSH and T4 may be normal.
- It is therefore essential to measure TSH, T4, andT3 in patients with symptoms of underactive thyroid.
HYPERTHYROIDISM - GRAVE’S DISEASE (DIFFUSE TOXIC GOITRE)
- The most common cause of primary hyperthyroidism in iodine-sufficient countries
- An autoimmune process in which thyroid stimulating antibody (TSAb), (also known as TSI, Trab, or LATS), binds with the TSH receptor on the thyroid, stimulating it to over produce thyroid hormones and to increase in size.
- Elevation of TSAb is present in 60-80% of cases and is diagnostic for Grave’s disease.
- Grave’s disease may be associated with a palpable diffuse goitre and general signs and symptoms of hyperthyroidism (as previously described)
SECONDARY HYPERTHYROIDISM - ACUTE SUPPURATIVE THYROIDITIS
- Due to bacterial infection
- Presents with fever, swelling and tenderness of the thyroid gland, lymphadenopathy and erythema of the skin over the gland.
- Associated with leucocytosis but thyroid hormone levels are usually within the reference ranges
- Acute suppurative thyroiditis requires antibiotic therapy prevent abscess formation, and possible surgery to drain any abscess that has formed.
OTHER CAUSES OF THYROIDITIS
Other causes of thyroiditis which cause hypo- or hyperthyroid include:
* Chronic Autoimmune thyroiditis
* Subacute thyroiditis
* Post-partum thyroiditis (discussed previously)
THE PARATHYROID GLAND - HYPOPARATHYROIDISM
Hypoparathyroidism is associated with parathyroid hormone (PTH) deficiency, which results in serum calcium deficiency (due to reduced osteoclastic activity, reduced vitamin D activation, and increased urinary calcium excretion)
THE PARATHYROID GLAND - HYPERPARATHYROIDISM
Hyperparathyroidism is associated with excessive secretion of parathyroid hormone, which results in elevated levels of plasma calcium due to:
* Increased calcium release from bone matrix,
* Increased calcium reabsorption by the kidney
* increased renal production of 1,25-dihydroxyvitamin D-3 (calcitriol), which increases intestinal absorption of calcium.
Insulin resistance
Two broad categories of presentation
- Type A –anti-insulin antibodies are absent, genetic category
- Type B –arises due to presence of anti-insulin antibodies, acquired category
Pro-inflammatory cytokines arising from excess adipose tissue (being overweight) negatively affect insulin action by promoting chemical activity in the intracellular environment that directly opposes insulin receptor signalling.
Consider it as an autoimmune disease…
This is perhaps the most useful aspect of insulin resistance, apart from diet, for herbalists to approach support and treatment. Salicylate containing plants may be most beneficial here
