Question

The endocrinologist you work for has prescribed thyroid hormones to each of the following adult patients. What
is the potential problem in prescribing thyroid hormones to each patient? What should be done to prevent the
problem in each case?

a.	Patient A is taking the drug Questran for high serum cholesterol.
b.	Patient B is on long-term Thorazine therapy for manic-depressive illness.
c.	Patient C is an insulin-dependent diabetic.
d.	Patient D takes oral contraceptives.
e.	Patient E had a heart attack 6 months ago.

Answer 1

a) There is a drug-drug reaction between Questran (cholestyramine) and thyroid hormone . Questran is a bile acid sequestrants that binds to and reduce the gastrointestinal absorption of thyroid hormones leading to increased levels of TSH and worsening hypothyroidism,

To prevent this, atleast thyroid hormone 4-6 hours should be taken prior to taking Questran.

b) Thorazine ( chlorpromazine ) which is a phenothiazine antipsychotic. when it is taken along with thyroid hormone it may cause thyroid function abnormalities, it decreases the response of TSH( thyroid stimulating hormone) response to TRH ( thyroid releasing hormone).

To prevent this, close monitoring of TSH levels and TCA levels for the development of thyroid function abnormalities.

c) Addition of thyroid hormone in patients with diabetes mellitus may worsen the glycemic control that results in increased insulin requirements.

To prevent the problem, regular blood glucose tests should be done and if necessary should increase the insulin dose.

d) Oral contraceptives when taken along with thyroid hormone causes increase in serum T.B.G (thyoxine binding globulin) which binds to thyroid hormones and results in less free thyroid hormones which leads to production of more T.S.H that futher requires the increase in thyroid hormone.

To prevent this, consider changes in T.B.G concentrations when interpreting T 4 and T3 values .Measure and evaluate the free or unbound thyroid hormone. if necessary discontinue the usage of oral contraceptives.

e) Thyroid hormones usually increaes heart rate,cardiac contractility, cardiac output. Thyroid replacement is usually beneficial to heart function but excess thyroid hormone causes increased heart rate, abnormal heart rhythms called atrial fibrillation.

To prevent this, periodic thyroid function tests to be done to check for excess thyroid hormone.