What Is Homeostasis?

Homeostasis is the body’s ability to adapt continuously — in order to maintain stable internal conditions despite external environmental shifts. At the heart of this intricate regulatory system lies the endocrine feedback loop — the foundational mechanism by which the body achieves and sustains homeostasis.

What is the Endocrine Feedback Loop?

As an endocrinologist, a clear understanding of endocrine feedback loops is paramount. These loops play a vital role in visualizing the endocrine system and, more importantly, in practicing endocrinology correctly.

Here’s How to Find the Best Thyroid Specialist in Rockville, MD

Feeling tired and sluggish all the time? Gaining weight? Experiencing dry skin and / or hair? These are all signs of a thyroid disorder. You need a medical expert in the field to help you feel better!

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.