Hemostasis in Hypothyroidism and Autoimmune Thyroid Disorders

Initial investigations revealed platelets of 238 (150–450), prothrombin time (PT) of 12.0 (12.0–17.0 s) and elevated activated partial thromboplastin time (APTT) of 41.0 (24.0–38.0 s). The elevation in APTT alluded to an intrinsic pathway abnormality which was investigated through further clotting factor analysis. This revealed reduced levels of chromogenic factor VIII 0.46 (0.6–1.3 U/dl), factor VIII clotting assay 0.4 (0.6–1.3 IU/ml), von Willebrand Factor antigen 0.31 (0.7–2.0 IU/ml) and von Willebrand Factor activity 0.39 (0.7–2.0 IU/ml). Initiation of thyroid hormone therapy prior to initiating glucocorticoid therapy may precipitate an acute adrenal crisis in patients with adrenal insufficiency. Treat patients with adrenal insufficiency with replacement glucocorticoids prior to initiating treatment with SYNTHROID see CONTRAINDICATIONS.

What Drugs, Substances, or Supplements Interact with Synthroid?

Because once you know you’re suffering from an underactive thyroid, you can take natural steps — including herbal remedies, and diet and lifestyle changes to restore your thyroid and feel better. Not all generic forms of Synthroid are created equal, which can create additional side effects, Goldfarb says. While most women tolerate the different generics just fine, some may have a reaction to the other ingredients used in the pills.

Recommended Dosage And Titration

The present report provides an updated and comprehensive report on hemostasis changes in hypothyroidism and autoimmune thyroid disorders. The recommended starting daily dosage of SYNTHROID in adults with primary, secondary, or tertiary hypothyroidism is based on synthroid doping age and comorbid cardiac conditions, as described in Table 1. For patients at risk of atrial fibrillation or patients with underlying cardiac disease, start with a lower dosage and titrate the dosage more slowly to avoid exacerbation of cardiac symptoms. Dosage titration is based on serum TSH or free-T4 see Important Considerations For Dosing.

Adverse Reactions In Pediatric Patients

Initiate appropriate supportive treatment as dictated by the patient’s medical status. Serum TSH levels should be monitored and the SYNTHROID dosage adjusted during pregnancy. Since postpartum TSH levels are similar to preconception values, the SYNTHROID dosage should return to the pre-pregnancy dose immediately after delivery see DOSAGE AND ADMINISTRATION. To minimize the risk of hyperactivity, start at one-fourth the recommended full replacement dosage, and increase on a weekly basis by one-fourth the full recommended replacement dosage until the full recommended replacement dosage is reached.

Oral levothyroxine sodium is a synthetic T4 hormone that exerts the same physiologic effect as endogenous T4, thereby maintaining normal T4 levels when a deficiency is present. Biotin supplementation is known to interfere with thyroid hormone immunoassays that are based on a biotin and streptavidin interaction, which may result in erroneous thyroid hormone test results. Stop biotin and biotin-containing supplements for at least 2 days prior to thyroid testing. Biotin supplementation may interfere with immunoassays for TSH, T4, and T3, resulting in erroneous thyroid hormone test results. Stop biotin and biotin-containing supplements for at least 2 days before assessing TSH and/or T4 levels see DRUG INTERACTIONS.

The “Stroke code” in the UK database did not specify subtype (94). The findings of an experimental study conducted on rats following injections of TRH, TSH, T3, and T4 subcutaneously for three days adds more confusion to the already contradictory results. TSH did not have any significant effect on factors II, VII, IX, X in rats, whereas TRH and T3 significantly reduced activities of the aforementioned factors. However, TRH, TSH, T3, and T4 each one individually prolonged aPTT and PT significantly, which suggests possible effects of these hormones on other factors in intrinsic and extrinsic coagulation pathways (73). These symptoms can all be related to a wide variety of medical conditions. An increased sensitivity to cold and hair loss can accompany hypothyroidism.

Elevated TAFI antigen levels were detected in overt hypothyroidism, suggesting fibrinolysis inhibition and levothyroxine treatment was effective in reducing these levels (65-67). TAFI antigen and activated TAFI (TAFIa) levels were significantly elevated in hypothyroid compared to control group patients and these levels decreased by levothyroxine therapy. The authors believe that fibrinolytic activity substantially decreases when hypothyroidism gets more severe and thyroid hormone therapy to restore euthyroidism may be important in ameliorating the increased risk of cardiovascular events (62). There is a census on a hypocoagulable state in overt hypothyroidism and a prothrombotic state in SCH and AIT. Figure 2 shows some of the changes in hemostatic parameters that may contribute to hypocoagulability in overt- and subclinical hypothyroidism.

Reading on Thyroid health

Some side effects of levothyroxine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Use In Specific Populations

Levothyroxine is generally continued for life in these patients see WARNINGS AND PRECAUTIONS. Titrate the dose of SYNTHROID carefully and monitor response to titration to avoid these effects see DOSAGE AND ADMINISTRATION. Consider the potential for food or drug interactions and adjust the administration or dosage of SYNTHROID as needed see DOSAGE AND ADMINISTRATION, DRUG INTERACTIONS and CLINICAL PHARMACOLOGY. SYNTHROID may reduce the therapeutic effects of digitalis glycosides. Serum digitalis glycoside levels may decrease when a hypothyroid patient becomes euthyroid, necessitating an increase in the dose of digitalis glycosides.

Closely monitor infants during the first 2 weeks of SYNTHROID therapy for cardiac overload and arrhythmias.
TSH may not normalize in some patients due to in utero hypothyroidism causing a resetting of pituitary-thyroid feedback.
Administration of sertraline in patients stabilized on SYNTHROID may result in increased SYNTHROID requirements.
The peak therapeutic effect of a given dose of SYNTHROID may not be attained for 4 to 6 weeks.
The higher affinity of both TBG and TBPA for T4 partially explains the higher serum levels, slower metabolic clearance, and longer half-life of T4 compared to T3.
Thrombin activates TAFI and activated TAFI (TAFIa) protects the fibrin clot against lysis (59), thus acting as a “Fibrinolysis inhibitor”.

Providing a complete list of medications to the doctor will help with getting the correct dose established for each individual patient. Synthroid is prescribed in tablets that range from 25 to 300 mcg in strength and is usually taken once a day with a full glass of water (about 8 ounces) 30 to 60 minutes before breakfast for best adsorption into the body. Children can take the medicine if the tablet is crushed and put into about 1 to 2 teaspoons of water; do not store or delay giving this crushed pill suspension. Doctors often may have to slowly increase the dose; patients should not increase or decrease this medication themselves. Because some preparations of the drug may contain iodine or lactose, patients should tell their doctors about such allergies or reactions to these components. Clumps of hair falling out, thin eyebrows, and problems with body hair are all signs of low thyroid function.