Thyroid Archives - GT health

FDA warning: biotin interferes with heart test

The FDA has now released a new warning against biotin interference with troponin, an essential heart blood test. Biotin or vitamin B7 is a water-soluble molecule found in many over-the-counter supplements such as multivitamins, prenatal, and in those that are meant to improve or protect the health of hair, skin, and nail.

Vitamin B7 is a central catalyst in many laboratory tests, especially those measuring troponin and thyroid hormone levels. When patients take high doses of biotin, especially >30 micrograms daily, it has the potential to underestimate the blood troponin concentration. Troponin measurements are critical in identifying adults with heart disease and particularly those having an acute event such as heart attack or myocardial infarction.

High doses of biotin intake, up to 300 mg daily, have been documented in patients with multiple sclerosis. These extraordinary doses may translate up to 1,200 ng/mL blood concentrations. Biotin has a short half-life of about two hours. It may be reasonable to suspend vitamin B7 intake for two to three days before undergoing any laboratory testing that incorporates biotin-analyte technology.

Patients, physicians, and laboratory personnel should be aware of possible interference of oral biotin with blood troponin and thyroid hormone testing, particularly in decisive clinical circumstances. A grave example would be a biotin user who presents clinically with a heart attack, and yet troponin measurements appear to be normal. Non-elevated troponin can lead to missed diagnosis and life-saving intervention.

New: Transoral Endocrine Surgery

About 250,000 thyroidectomies and parathyroidectomies are conducted yearly in the United States. The typical thyroid or parathyroid surgery is performed via the front of the neck. These operations are done mainly for thyroid enlargement, nodules, cancer, and parathyroid masses. Although conventional surgeries are effective and safe, they have one disadvantage in common: they leave an undesirable visible scar for many patients.

To avoid the neck scar, surgeons introduced the concept of transoral endocrine surgery (TES) in 2011. The first operation was performed in the United States, Apr 2016. Since then, more than 300 transoral operations have been conducted in the U.S. alone. The main surgical route was achieved via the upper lip, otherwise called the “endoscopic vestibular approach.”

To date, the reported experience has shown that the safety of TES is similar to the traditional operations for the following outcomes: recurrent laryngeal nerve injury, hypoparathyroidism, and rate of infections. Based on standard inclusion and exclusion criteria, authors have found that 56% of all patients undergoing thyroidectomy or parathyroidectomy are eligible for TES.

The two most common conditions qualified for transoral endocrine surgery were thyroid nodules (76%) and parathyroid adenomas (58%). TES has the potential to be performed in the 100,000s of individuals annually. However, the authors’ findings need to be formally tested and validated before the mass application of the operation.

Thyroid hormones supplementation in pregnant women with Hashimoto’s thyroiditis

Thyroid hormones supplementation 50 mcg daily did not improve pregnancy outcomes in women with Hashimoto’s thyroiditis in the presence of normal thyroid function. Hashimoto’s thyroiditis was confirmed by elevated TPO antibodies at study entry. About 1,000 pregnant women were followed through full term.

This is an important study as it defies the current medical opinion of poorer pregnancy outcomes in euthyroid Hashimoto’s thyroiditis.

Thyroid cancer: low-dose radioactive iodine works in the long term too

Now we have long-term data from the original HiLo trial. Patients with no distant metastasis, well-differentiated thyroid carcinoma do as well with low-dose radioactive iodine (30 mCi) treatment compared to those receiving the high dose RAI (100 mCi).

Unless distant metastasis is documented, patients with well-differentiated papillary or follicular cancer should receive 30 mCi I-131 when indicated. A group of 450 patients was followed for about 7 years.

Thyroid supplementation in heart failure

This 5-year observational study shows that thyroid hormone supplementation increases major adverse cardiovascular events (MACE), cardiovascular death, and all-cause mortality in patients with heart failure. Indirectly, this is in accordance with the well-documented benefits of beta-adrenergic receptor blockade in persons with cardiac failure.

Clinically, in patients with concomitants hypothyroidism and heart failure, thyroid hormone supplementation should be started at a low dose, increased slowly, and aiming a higher TSH target than in general population.

The lost Woltman’s Sign of Hypothyroidism

A nice academic demonstration of the Woltman’s sign in a patient with profound hypothyroidism, who’s TSH was 200 mIU/L. Delayed relaxation of the ankle reflex normalized as TSH improved with proper thyroid hormone supplementation. The Woltman’s sign could be useful if thyroid laboratory testing is not available and the patient’s baseline ankle reflex is known.

Pituitary enlargement due to hypothyroidism

Another nice report of total pituitary enlargement due to the long-standing untreated primary hypothyroidism. Low levels of FT3 and FT4 lead to excessive TRH and TSH production, in turn causing pituitary expansion.

This case is unique as it is found in a child suffering from growth retardation. Proper treatment with thyroid hormone supplementation reversed the illness.

Subclinical hypothyroidism in the elderly

Personalized therapy is crucial in good clinical practice, and in the management of older patients with subclinical hypothyroidism, multiple factors must be considered, including age-dependent TSH cutoffs, thyroid autoimmunity, the burden of comorbidities, and the possible presence of frailty.

Levothyroxine is the drug of choice for the treatment of hypothyroid older people, but the risk of overtreatment, potential adverse drug reactions, and patient compliance should always be considered and thyroid status periodically reassessed.

JES

New FDA approval: drug therapy for anaplastic thyroid cancer

Anaplastic thyroid cancer (ATC) is a rare and aggressive type of thyroid cancer. It accounts for about 1-2% of all thyroid cancers. NIH estimates 54,000 new cases of thyroid cancer and 2,000 deaths from the disease in the US in 2018.

The tafinlar + mekinist combination is now approved for the treatment of BRAF V600E mutation-positive ATC that cannot be addressed surgically or has already spread to other organs. Tafinlar and Mekinist have also been approved for two other BRAF V600 mutation-positive metastatic malignancies; melanoma and non-small cell lung cancer.

Cancer immunotherapy causes hypothyroidism

Nivolumab is an effective immunotherapy for advanced malignancies such as gastric cancer, renal cell carcinoma, unresectable metastatic melanoma, non-small cell lung cancer, hodgkin lymphoma and head/neck cancer. However it has also been noted to cause endocrinopathies like type 1 diabetes and pituitary, adrenal and thyroid dysfunctions.

Current study shows that nivolumab-induced inflammatory hypothyroidism is relatively rare at about 5% in 6 months, and was mainly seen in participants with elevated baseline thyroid antibodies. This suggests that the anti-PD1 monoclonal Ab therapy causes hypothyroidism in predisposed individuals, thus initial evaluation of TPO and Tg antibodies may be warranted prior to starting nivolumab.

Hyperthyroid and ventricular fibrillations

This case shows a positive correlation between thyroid levels and J-wave amplitude in a patient experiencing ventricular fibrillations. Pronounced J-waves in multiple EKG leads can predict lethal arrhythmias, thus early diagnosis and treatment are necessary. More research would be needed however to clarify or solidify the cause-effect dance between hyperthyroidism and elevated J-waves.

Congenital malformations in Grave’s disease

Traditional approach is to use propylthiouracil (PTU) for Grave’s disease during the first trimester. This article points otherwise, that both methimazole and PTU can increase the risk of congenital malformations when used in the first three months of pregnancy. I suspect more research would be needed before changing guidelines or standard of care.