A 22-year-old woman comes to the office to discuss initiating oral contraception. She has been sexually active with the same partner for the last year and has been using condoms but would like a more reliable method of contraception. The patient has a 4-year history of primary hypothyroidism, which has been well controlled on 125 µg/day of levothyroxine. Her most recent serum TSH was within normal limits. She has no other chronic medical conditions and no previous surgeries. The patient does not use tobacco, alcohol, or illicit drugs. Family history is significant for breast cancer in her mother diagnosed at age 52 and a sister who has type 1 diabetes mellitus. Blood pressure is 110/76 mm Hg and pulse is 78/min. BMI is 24 kg/m². There is no thyromegaly, and the remainder of the physical examination is normal. The patient states that her best friend noted an improvement in her acne after starting an oral contraceptive, and she would like to take the same type of pill. Which of the following is the most accurate statement regarding contraception in this patient?

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Quizplus · Accepted Answer

Explanation: 11ec2b69_bed0_388c_8f63_97d0bfc56b17_MD0005_00 More than 99% of circulating thyroid hormone (T4, T3) is bound to plasma proteins, primarily thyroxine-binding globulin (TBG). Biologically active, free thyroid hormone is rapidly cleared by the kidneys, and binding proteins ensure that adequate hormone is available for delivery to the peripheral tissues. Elevated estrogen levels, as seen in pregnancy and patients taking oral contraceptives, stimulate hepatic synthesis of TBG. Patients with normal thyroid function can increase thyroid hormone production to saturate the additional protein binding sites, but those with primary hypothyroidism are unable to increase thyroid hormone synthesis; oral contraceptive use in these patients can induce a relative hypothyroid state. Most patients with hypothyroidism will require an increased dose of levothyroxine when starting oral contraceptives or becoming pregnant (Choice D). Serum TSH should be checked several weeks after initiating an oral contraceptive, with the levothyroxine dose increased as needed to maintain TSH within the normal range. Due to the risk of hypothyroid complications early in pregnancy, pregnant patients warrant even more aggressive management; the levothyroxine dose should be increased by approximately 30% (eg, 2 additional tablets a week) immediately following a positive pregnancy test and TSH checked every 4-6 weeks thereafter. (Choices A and C) There is a slightly increased risk of venous thromboembolism in women taking estrogen-containing oral contraceptives, but the risk is not further increased due to hypothyroidism. Hypothyroidism is not a contraindication to oral contraceptives (and the estrogen dose does not need to be altered) provided the dose of levothyroxine is properly adjusted. (Choice B) Progestin-only contraceptives (ie, "mini-pills") are indicated for patients with contraindications to estrogen (eg, venous thromboembolism) but are less effective in preventing pregnancy than combined oral contraceptives. Educational objective: Patients with hypothyroidism may require an increased dose of levothyroxine following initiation of estrogen-containing oral contraceptives due to an increase in thyroxine-binding globulin. Patients should have TSH measured several weeks after initiation of oral contraceptives, with the dose of levothyroxine adjusted to maintain TSH in the normal range. References: Effects of a monophasic combined oral contraceptive containing nomegestrol acetate and 17ß-oestradiol in comparison to one containing levonorgestrel and ethinyl estradiol on markers of endocrine function. (http://www.ncbi.nlm.nih.gov/pubmed/21942708) Effects of the environment, chemicals and drugs on thyroid function. (http://www.ncbi.nlm.nih.gov/pubmed/25905415)

A 22-Year-Old Woman Comes to the Office to Discuss Initiating