Pituitary and Thyroid Flashcards
Drugs affecting the thyroid
Iodine and potassium iodide
Liothyronine (T3) and Levothyroxine (T4) both treat hypothyroidism. Long half life. 1x per day dose.
Methimazole and propylthiouracil both tx hyperthyroidism. Inhibit production of T3 and T4, but no effect on T3 and T4 already stored. short half life. Multiple day dosing.
Somatropin vs somatostatin
Stomatropin- Growth Hormone
Somatostatin- GHIH
Gonadotropin
LH and FSH
Gonadorelin
Gonadotropin releasing hormone (from the hypothalamus)
Must be released in pulse doses.
Continuous dose causes negative feedback.
Synthetic compounds of GnRH
Leuprolide
Gonadorelin
Nafrelin
Hypersecretion of GH/somatropin causes
Gigantism- proportional
Acromegaly- disproportional
Under secretion causes dwarfism.
Prolactin secretion is inhibited by
dopamine
Post pit
Extension of the hypothalamus. NOT a separate organ. Secretes vasopressin (ADH) and oxytocin.
The vasopressin and oxytocin precursors are synthesized by hypothalamus and stored in the posterior pituitary. NOT regulated by releasing hormones.
Can you give any pituitary hormones orally?
NO! Not ant or post. most are proteins/peptides
Does the anterior pit synthesize its own hormones? what about posterior
Anterior- synthesizes own. Does not store.
Posterior- stores from hypothalamus and then releases.
Signs of hypothyroidism
Brady, cold intolerance, mental and physical slowing.
Dx: elevated TSH
Tx: T3 or T4 (liothyronine T3, Levothyroxine T4)
Signs of hyperthyroidism
Tachy, excess heat production, increased metabolism.
Dx: Decreased TSH.
Tx: Methimazole or propylthiouracil. Inhibits production of T3 and T4. or surgical removal. Pt may develop hypothyroidism after surgery.
Drugs that induce the P450 system accelerate the metabolism of
Thyroid hormones. T3 and T4.
6 hormones released by anterior pituitary
TSH LH FSH GH Prolactin ACTH
5 hormones released by the hypothalamus
Thyroid releasing GnRH corticotropin releasing hormone GHRH GHIH
*2 for GH, none for prolactin.
Proteins and peptide hormones
Insulin, LH, oxytocin, angiotensin II
GHIH does what
Suppresses GH and TSH release
Also inhibits release of insulin, glucagon, and gastrin.
Used to tx tumors that are reliant on GH
How can GnRH be used to suppress gonadal hormones?
If released continuously. Can treat prostate cancer, endometriosis
How are hormones of the posterior pituitary regulated?
Not regulated by releasing hormones. Released in response to specific physiological signs.
When can oxytocin be used to induce labor
Only full term
Vasopressin causes increased water reabsorption in the kidney (tx diabetes insipidus) and causes constriction of vascular smooth muscle.
What is a modified version that does not constrict vascular smooth muscle?
Desmopressin
TSH release from ant pit results in
Uptake of iodide and synthesis of t3 and t4 –> released into the blood.
T3 and T4 are bound to plasma proteins upon release, (inactive) They must dissociate from protein before entering cell.
T4 is enzymatically changed to t3 by the cell. Regulates gene expression.
Admin of T3 and T4/
Well absorbed after oral admin. Drugs that induce the p450 system accelerate metabolism of the thyroid hormones.
How to treat thyroid storm (hyperthyroidism)
Beta blockers to stop sympathetic stimuluation
Same therapy, but more aggressive.
dose of iodide inhibits the production of hormone. but this only lasts a few days.
