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Thyroid Disorders

Chronic dieting can result in a significant decrease in intracellular and circulating triiodothyronine (T3) levels [50-52], which drastically reduces basal metabolic rate by 15%-40%. This is an adaptive measure the body takes to conserve energy according to Denis Wilson, MD [53]. Thyroid levels and metabolism stay in a starvation mode making weight loss difficult.

Various studies found that T3 levels were significantly decreased with no difference in thyroid stimulating hormone (TSH) and thyroxine (T4) levels (therefore not able to be detected by routine TSH testing) [54,55]. The reduced T3 may contribute to fatigue and depression expressed by many bariatric surgery candidates. Many of these people have difficulty keeping weight off and are not excessive eaters. Unless the thyroid dysfunction is corrected, weight loss may be far less from the surgery than needed to correct metabolic issues.

Croxson and Ibbertson found that individuals with a history of intense dieting had dramatic reductions in T4 to T3 conversion that led to an intracellular deficiency of T3 that a TSH and T4 test failed to detect [56]. According to Dr. Wilson [53], numerous studies have shown that insulin resistance, diabetes, and metabolic syndrome are associated with reduced T4 to T3 conversion, an intracellular deficiency of T3, and an increased conversion of T4 to reverse T3 (rT3) [57-59].

Hashimoto’s thyroiditis (also called chronic lymphocytic thyroiditis) is an autoimmune disorder [60] and is considered the most common cause of thyroid problems in the United States. Hashimoto’s disorder is usually diagnosed between the ages of 30 and 50 with more women than men affected, usually as a result of a goiter. Antithyroglobulin antibodies (anti-TG) are elevated in more than 90% of the patients [61] while patients with elevated thyroid peroxidase antibodies (anti- TPO) may be asymptomatic until the disease progresses further.

Nutritional status of bariatric surgery patients can also play a role in hypothyroidism development. Vitamins A, E, B12, riboflavin, and niacin deficiency plus inadequate selenium, iodine, iron, zinc, and potassium can alter the metabolism of T4 to T3 in peripheral tissues [62-64]. Excess consumption of goitrogenic foods—cabbage, kale, Brussels sprouts, cauliflower and soy—can induce hypothyroidism.

Since obesity is directly associated with thyrotropin (TSH) and thyroid function, comprehensive thyroid testing needs to be considered since imbalances can affect virtually every metabolic process in the body from mood to energy level. Common symptoms caused from hypothyroidism are

  • • Fatigue
  • • Decreased heart rate
  • • Progressive hearing loss
  • • Weight gain
  • • Problems with memory and concentration
  • • Depression
  • • Goiter (enlarged thyroid gland)
  • • Muscle pain or weakness
  • • Loss of interest in sex
  • • Numb, tingling hands
  • • Dry skin
  • • Swollen eyelids
  • • Dryness, loss or premature graying of hair
  • • Extreme sensitivity to cold
  • • Constipation
  • • Irregular menstrual periods
  • • Hoarse voice

A comprehensive thyroid assessment includes: high-sensitivity thyroid stimulating hormone (hTSH), free serum thyroxine (fT4), free triiodothyronine (fT3), rT3, anti-TG, and anti-TPO.

Several studies have been reported about the weight loss after bariatric surgery influencing thyroid hormone regulation possibly through the decreasing leptin influence on peripheral hormone metabolism [65]. Weight loss after RYGB increased free thyroxine (T4) with no change in TSH concentration [66] but Alagna et al. [67] reported decreased fT3 postsurgery and proposed it as a result of reduced peripheral conversion of T4 to fT3.

Subclinical hypothyroidism defined as elevated TSH is consistent in some morbidly obese patients and resolves after bariatric surgery [68,69]. Fazylov studied 20 morbidly obese females who underwent RYGB while on thyroid replacement therapy and found 5 of the 20

had worsened hypothyroidism postsurgery. These cases were identified as having thyroid autoimmune disease [70].

Absorption of levothyroxine, used for the treatment of hypothyroidism, is affected by many factors. The pharmacokinetics in Gkotsina’s review of thyroid replacement absorption indicates that the stomach, duodenum, and upper part of the jejunum are not sites of T4 uptake because RYGB and SLG patients had no alteration in absorption postsurgery [71].

A liquid formulation for treatment of hypothyroidism postbariatric surgery is available [72] but Michalaki et al. report that iodine, which is essential for the synthesis of thyroid hormones, should be considered for supplementation [73] in addition.

Sleeve gastrectomy evaluation on patients with normal thyroid function presurgery indicated a decrease in TSH and steady levels of fT4 during their weight loss [74].

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