You have been assigned to care for Ms. A, who is 28 years old. She came to her primary care provider with complaints of lethargy and fatigue. She states that she is a single mother of a 2-year-old son and that it takes all her energy just to get through the day. She also complains of being cold all the time and of wanting to sleep, and she is very concerned about a sudden loss of hair. She seems to be having difficulty communicating her concerns to the healthcare provider and frequently repeats herself. During her physical examination, the primary care provider notes the following: BP 120/68, HR 70, RR 12, T 97.8° F. Ms. A's face is pale, puffy, and expressionless. Her skin is cold and dry, and her hair is brittle. Her thyroid gland is enlarged. Ms. A's current medications include sertraline (Zoloft) for depression and ferrous sulfate for anemia, as well as sucralfate (Carafate) for peptic ulcer disease.
The primary care provider determines that Ms. A has hypothyroidism and orders a pregnancy test for her because she cannot recall the time of her last menstrual period. Ms. A wants to know why this is so important. She states, "I know I'm not pregnant. I have been very careful since the birth of my son." What is your most appropriate response? What medication interactions, if any, would you anticipate in this case with initiation of thyroid hormone replacement therapy?