Stop oral therapy and start later: This is a new perspective for hypothyroid patients who need lifelong intravenous levothyroxine

Zafer Pekkolay

doi:10.1530/endoabs.81.EP1154

Introduction: Although the replacement route is oral in most hypothyroid patients, euthyroidism cannot be achieved with oral therapy in some patients rarely (1). Although oral levothyroxine is used above the standard dose (1.6-1.9 mg/kg/day), there is resistance to oral therapy if there are laboratory and clinical signs of hypothyroidism (2). Crushing the drug and using it with vitamin C increases the absorption of levothyroxine (3). Rarely, some patients require lifelong intravenous levothyroxine.

Case report: Total thyroidectomy was performed in a 60-year-old female patient in 2014, after thyroid nodule FNAB result was found to have AUS. Its pathology was reported as medullary thyroid cancer. Despite increasing oral doses of levothyroxine after surgery, the patient with severe hypothyroidism had a negative pseudomalabsorption test, a negative celiac panel, and a negative Helicobacter pylori antigen. Although the patient was given high doses of levothyroxine and lioiodotroin, his hypothyroidism did not improve. Combining levothyroxine with vitamin C/acid drinks and crushing the levothyroxine tablet did not ameliorate hypothyroidism. Euthyroidism was achieved with intravenous levothyroxine 200 mg/session three times a week (Table 1). Due to a change in our healthcare system, the patient could not receive intravenous treatment for about two months. The patient drank 450 micrograms of levothyroxine to overcome this problem by dissolving it in tap water. The patient’s thyroid function tests, who came to the outpatient clinic in the first month of this treatment, were euthyroid. Euthyroidism was observed again in the patient who used the treatment he received for one more month (Table 2).

Table 1 Patient’s history summary
Age (year), Gender	60, Female
Hypothyroidism etiology	Medullary Thyroid Cancer
Duration of hypothyroidism (year)	7
Levothyroxine dose	600 mg/week/intravenous
Pseudomalabsorption	Negative
Celiac panel	Negative
Helicobacter pylori antigen	Negative
LT4+LT3	No-response
LT4 intake with vitamin C/sodas	No-response

Table 2 Oral levothyroxine only (450 mcg/day)
	1st month of treatment	2nd month of treatment
TSH (mU/l) (0,27-4,2)	0,7	0,88
Free T3(ng/dL) (0,93-1,7)	0,8	1,0
Free T4(pg/mL) (2,0-4,4)	1,8	2,0

Comment and new perspective: The patient, who needed a total of 600 mg intravenous per week for seven years, switched to oral therapy because intravenous therapy could not be performed. Clinical response was obtained from the patient. In patients who do not respond to oral therapy in the first period, oral therapy can be tried later. This may indicate that intestinal levothyroxine absorption may increase after oral levothyroxine absorption is not taken for a while.

Keywords refractory hypothyroidism, switching, levothyroxine:

Endocrine Abstracts

EP1154