Drug-Induced Nutrient Depletions: What Pharmacists Need to Know

The information is made available with the understanding that the author and publisher are not providing medical, psychological, or nutritional counseling services on this site. The information should not be used in place of a consultation with a competent health care or nutrition professional. No matter how much you already know, it’s important to keep learning about your condition. The better you understand hypothyroidism, the better prepared you are to manage it.

Interestingly, the patients that received 2 years of levothyroxine replacement therapy had lower bone density. Thus, simultaneous treatment of hypothyroidism and bone loss seems to be necessary. However, it has been shown in children with congenital hypothyroidism that bone density is lower than normal children.39 In children with subclinical hypothyroidism, bone qualities by using of quantitative ultrasound were studied. The results showed that with increasing concentrations of TSH, calculated osteo sono-assessment index is reduced.40 This study showed that the hypothyroidism affects the bone structure. In young or middle-aged patients who are otherwise healthy, the starting dose of levothyroxine can be 100 mcg or 1.7 mcg/kg orally once a day. Signs and symptoms are nonspecific and can vary in individual presentations (Table 2 and Table synthroid tests 31,3,10).

These deficiencies can contribute to side effects experienced with oral contraceptives.5 Pancreatic enzymes can reduce absorption of folic acid and are another common medication that causes deficiency. Some patients may require supplementation.10 Pharmacists should use drug-information resources for each anticonvulsant to understand its interaction with folic acid and subsequent management. In patients with heart disease, therapy is begun with low doses of levothyroxine, usually 25 mcg once a day. The dose is adjusted every 6 weeks until maintenance dose is achieved. The maintenance dose may need to be increased in patients who are pregnant.

Hypothyroidism from head to toe*

You should refer to the prescribing information for Synthroid for a complete list of interactions. SYNTHROID is not indicated for suppression of benign thyroid nodules and nontoxic diffuse goiter in iodine-sufficient patients, as there are no clinical benefits and overtreatment with SYNTHROID may induce hyperthyroidism. Following a 25-mcg dose change of levothyroxine, most patients had changes in TSH levels.

Understanding possible side effects

In order for Synthroid to be effective, it should always be taken the same way every day. This is important because the amount of medicine you need is very precise. And even the way you take Synthroid can affect how much medicine your body is getting.

Patient resources

Hypothyroidism may also occur in patients taking amiodarone or other iodine-containing drugs, in patients taking interferon-alfa, and in patients being treated for cancer with checkpoint inhibitors or some tyrosine kinase inhibitors. Throughout your lifetime, your doctor may have to adjust your dose of Synthroid. That’s because the amount of thyroid hormone your body needs may change. Some of the reasons for this may include major life events like pregnancy or menopause, or aging.

The hypothalamus adjusts the release of thyrotropin-releasing hormone based on circulating levels of thyroid hormone. Together, these hormones regulate the secretion of TSH from the anterior lobe of the pituitary gland. This functioning feedback loop keeps the blood level of the thyroid hormone normal. Older patients have significantly fewer symptoms than do younger patients, and symptoms and signs are often subtle and vague. Many older patients with hypothyroidism present with nonspecific geriatric syndromes—confusion, anorexia, weight loss, falling, incontinence, and decreased mobility. Musculoskeletal symptoms (especially arthralgias) occur often, but arthritis is rare.

• The dose used should be the lowest that restores serum TSH levels to the midnormal range (though this criterion cannot be used in patients with secondary hypothyroidism).
• If you are elderly and are just starting treatment for hypothyroidism, your doctor may start you on a lower dose of medicine.
• Since thyroid hormone occurs naturally in the body, almost anyone can take levothyroxine.

It is important to note that specific criteria to label interactions as “clinically significant” have not been established, although a threshold of ≥20% change in the kinetic and/or dynamic parameter of the drug or nutrient has been proposed (1). Long-term use of the drug is often needed to reach such a threshold and for clinical symptoms of the drug-nutrient interaction to manifest (1). Although drug-nutrient interactions have not been systematically studied, there are a number of known interactions reported in the scientific literature. The interactions listed in Table 1 are not meant to be comprehensive but include some of the more common clinically relevant drug-nutrient interactions, especially in the context of micronutrient inadequacy. For additional references on drug-nutrient interactions, see Table 2.

Most patients with subclinical hypothyroidism do not benefit from treatment unless the thyroid-stimulating hormone level is greater than 10 mIU per L or the thyroid peroxidase antibody is elevated. SYNTHROID® (levothyroxine sodium) tablets, for oral use is a prescription, man-made thyroid hormone that is used to treat a condition called hypothyroidism in adults and children, including infants. It is meant to replace a hormone that is usually made by your thyroid gland. SYNTHROID should not be used to treat noncancerous growths or enlargement of the thyroid in patients with normal iodine levels, or in cases of temporary hypothyroidism caused by inflammation of the thyroid gland (thyroiditis). Another commonly used medication that can result in folate deficiency is estrogen. It reduces absorption of folic acid and increases excretion as well.

Do not share this medicine with another person, even if they have the same symptoms you have. It may take several weeks before your body starts to respond to Synthroid. Follow all directions on your prescription label and read all medication guides or instruction sheets. The Linus Pauling Institute’s Micronutrient Information Center provides scientific information on the health aspects of dietary factors and supplements, food, and beverages for the general public.