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pituitary and thyroid
pituitary and thyroid

Additional Pharmacology Flashcards





 List the hormones of the anterior and posterior pituitary. How is the regulation of vasopressin and oxytocin different from that of other pituitary hormones?


Hormones of the anterior pituitary: growth hormone, adrenocorticotropic hormone, thyrotropin-stimulating hormone, luteinizing hormone, follicle-stimulating hormone, prolactin

Hormones of the posterior pituitary: oxytocin, arginine vasopressin (AVP) or ADH.

The posterior pituitary hormones (vasopressin & oxytocin) unlike anterior pituitary hormones are not regulated by hypothalamic releasing hormones. They are synthesized in the hypothalamus, transported by carrier proteins to the posterior pituitary where they are stored and released directly into the systemic circulation in response to specific physiologic signals, such as high plasma osmolarity or parturition.

Compare and contrast vasopressin and desmopressin.

Desmopressin is a modified form of the normal human hormone vasopressin. Vasopressin agonists are used therapeutically in various conditions, and its long-acting synthetic analogue desmopressin is used in conditions featuring low vasopressin secretion, as well as for control of bleeding and in extreme cases of bedwetting by children. Desmopressin is degraded more slowly than recombinant vasopressin, and requires less frequent administration. In addition, it has little effect on blood pressure, while vasopressin may cause arterial hypertension.

Good answer. Note that "for control of bleeding", desmopressin improves the action of dysfunctional platelets. In bleeding patients who have platelet dysfunction associated with aspirin, uremia or several other causes, desmopressin may help you avoid transfusing blood products.

Describe the indications for desmopressin and the role of desmopressin in managing bleeding.

Desmopressin (DDVAP) is a derivative of the anti-diuretic hormone. It can be use to promote the release of vWF (von Willebrand factor) levels from endothelial storage sites, increasing exposure at damaged sites. It also increases the density of platelet surface glycoprotein receptors (improving adhesiveness) and increases plasma activity of Factor VIII and levels of plasminogen activator antigen. It is used in patients with coagulation disorders such as von Willebrand disease, mild hemophilia A (factor VIII deficiency), and with thrombocytopenia. It has been used prophylactically in patients undergoing surgery characterized by large blood loss and transfusion requirements.

Desmopressin shortens the prolonged APTT and shortens the bleeding time. These effects result from the increases in factor VIII and vWF (from storage sites), which play a rate-accelerating role of intrinsic coagulation and primary hemostasis.

Desmopressin can also be used for the treatment of diabetes insipidus and nocturnal enuresis.
It is not for the treatment of hemophilia B (factor IX deficiency) or severe hemophilia A. Desmopressin can result in water retention and hyponatraemia.

Briefly describe how you would diagnose and manage hyperthyroidism?

Thyroid function tests include: T4 level and TSH level.


Diagnosis of hyperthyroidism: Increased T4, TSH  decreased (through negative feedback.

Signs are: goiter, tachycardia, proptosis, atrial fibrillation, weight loss, and muscle weakness.
Symptoms are: anxiety, tremor, heat intolerance, fatigue.

Management of hyperthyroidism has three approaches:
1. Antithyroid drugs, such as propylthiouracil (PTU) inhibit iodination and coupling reactions in the thyroid gland, thus reducing production of T3 and T4. PTU also inhibits peripheral conversion of T4 and T3. Iodine in large doses not only blocks hormone production, but it also decreases the vascularity and size of the thyroid gland, making iodine useful in preparing hyperthyroid patients for thyroid surgery.
2. Radioactive Iodine, is actively concentrated by the thyroid gland, resulting in destruction of thyroid cells and a decrease in the production of hormone.
3. Surgical subtotal thyroidectomy

 * * All of these approaches may render the patient hypothyroid * *

Don't forget about beta-blockers. Tachycardia in hyperthyroid patients should be controlled with beta-blockers. In the case of thyroid storm, administer propranolol preoperatively until HR is ~ 85 bpm or less. - JM


Briefly describe the pharmacology of propylthiouracil (PTU).

PTU is a thioamide drug used to treat hyperthyroidism by decreasing the amount of thyroid hormone produced by the thyroid gland.


Side effects include a risk of agranulocytosis. PTU inhibits the enzyme, thyroperoxidase which normally acts in thyroid hormone synthesis by oxidizing the anion iodide to iodine, facilitating iodine’s addition to tyrosine residues on the hormone precursor thyroglobulin. PTU does not inhibit the action of the sodium-dependent iodide transporter located on follicular cells' basolateral membranes. Inhibition of this step requires competitive inhibitors, such as perchlorate and thiocyanate. PTU also acts by inhibiting the enzyme 5'-deiodinase, which converts T4 to the active form T3.


Briefly describe how you would diagnose and manage hypothyroidism?

Diagnosis of hypothyroidism is based on history, physical exam and laboratory tests. It is confirmed by a low serum free T4 level; primary hypothyroidism is differentiated from secondary disease by an elevation in serum TSH level.

Hypothyroidism is treated by replacement therapy with synthetic preparations of T4 (levothyroxine), or T3 (liothyronine), or both. Most people are treated with T4. Serum TSH levels are used to estimate the adequacy of T4 replacement therapy. When the TSH level is normalized, the T4 dosage is considered satisfactory (for primary hypothyroidism only). Levothyroxine has a long half life, thus given once daily. Steady state is achieved in 6 to 8 weeks. A “go low and go slow” approach should be considered in the treatment of elderly with hypothyroidism because of the risk of inducing acute coronary syndromes in susceptible individuals.

Note low T4 and high TSH

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