Synthroid Levothyroxine Sodium: Side Effects, Uses, Dosage, Interactions, Warnings

These include urticaria, pruritus, skin rash, flushing, angioedema, various GI symptoms (abdominal pain, nausea, vomiting and diarrhea), fever, arthralgia, serum sickness and wheezing. Because of the increased prevalence of cardiovascular disease among the elderly, initiate SYNTHROID at less than the full replacement dose see DOSAGE AND ADMINISTRATION and WARNINGS AND PRECAUTIONS. Published studies report that levothyroxine is present in human milk following the administration of oral levothyroxine.

Adverse Reactions In Pediatric Patients

Pineal melatonin can also directly modulate the sensitivity of the SCN to zeitgebers, thereby influencing the overall stability and adaptability of the circadian system. The two melatonin receptors (MT1 and 2) are found in various tissues and organs36. G-protein coupled receptor binding of melatonin activates different signal cascades that can also affect gene transcription37.

The «optimal dose» was determined for each patient as that dosage of thyroxine being taken when the thyrotropin releasing hormone (TRH) response was normal (ie, an increase in TSH of between 4.7 and 25 mIU/L). Recent findings suggest that estrogen modifies the SCN rhythm through astrocytes rather than neurons, specifically targeting their gap junctions and restoring rhythmicity after AVP receptor inhibition. In vitro studies show that females with high estrogen levels, resembling the proestrus phase of the estrous cycle, exhibit robust rhythmicity in the SCN, potentially mediated through astrocytic gap junctions as shown in vitro89,92. This implies that estrogen stabilizes the central clock’s rhythmicity, preventing it from responding to acute external cues. In contrast, ARs in the male SCN core receive direct light signals from the retinohypothalamic tract93, suggesting that testosterone influences the SCN phase in response to light cues. You may not be able to take Synthroid if you have certain medical conditions.

Finally, it has been demonstrated that the adrenal cortex expresses a functional circadian clock, which gates the organ’s sensitivity to ACTH and further contributes to the generation of a robust GC rhythm10,49.
If the T4 and TSH levels are normal, euthyroidism may be assumed and, therefore, the hypothyroidism can be considered to have been transient.
Administration of sertraline in patients stabilized on SYNTHROID may result in increased SYNTHROID requirements.
Do not administer in foods that decrease absorption of SYNTHROID, such as soybean-based infant formula.
Therefore, a decrease in the dose of anticoagulant may be warranted with correction of the hypothyroid state or when the SYNTHROID dose is increased.

Administration

Use the serum free-T4 level to titrate SYNTHROID dosing until the patient is clinically euthyroid and the serum free-T4 level is restored to the upper half of the normal range see Dosage and Administration (2.3). Use the serum free-T4 level to titrate SYNTHROID dosing until the patient is clinically euthyroid and the serum free-T4 level is restored to the upper half of the normal range see Recommended Dosage And Titration. SYNTHROID is indicated in adult and pediatric patients, including neonates, as a replacement therapy in primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) congenital or acquired hypothyroidism. Use the serum free-T4 level to titrate SYNTHROID dosing until the patient is clinically euthyroid and the serum free-T4 level is restored to the upper half of the normal range. Circulating thyroid hormones are greater than 99% bound to plasma proteins, including thyroxine-binding globulin (TBG), thyroxine-binding prealbumin (TBPA), and albumin (TBA), whose capacities and affinities vary for each hormone. 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.

Since THs are largely arrhythmic, they can hardly act as rhythm drivers or zeitgebers. However, by interacting with intrinsic rhythmic signals changes in TH levels can affect downstream functions such as gene expression rhythms. Candidates for such intrinsic rhythms would be hormone transport (uptake), metabolization (deiodinases), and/or receptor activation (THRα and THRβ), leading to an integrated rhythmic response26. In line with this, the hepatocyte sensibility to T3 treatment is time-of-day dependent (e.g., gated) – at least in vitro105. The function as rhythm driver is clock-independent and requires a rhythmic hormone that can influence rhythmic gene expression via direct hormone-target interactions. As a zeitgeber, hormones directly regulate clock gene expression in target tissues and can shift the phase of the clock.

Drug Summary

Seizures occurred in a 3-year-old child ingesting 3.6 mg of levothyroxine. Symptoms may not necessarily be evident or may not appear until several days after ingestion of levothyroxine sodium. The signs and symptoms of overdosage are those of hyperthyroidism (see PRECAUTIONS and ADVERSE REACTIONS). Levothyroxine, at doses individualized according to patient response, is effective as replacement or supplemental therapy in hypothyroidism of any etiology, except transient hypothyroidism during the recovery phase of subacute thyroiditis. The signs and symptoms of overdosage are those of hyperthyroidism see WARNINGS AND PRECAUTIONS and Adverse Reactions.

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.
NP Thyroid is used for hashimoto’s disease, hypothyroidism, after thyroid removal, thyroid cancer …
SYNTHROID should be taken at least 4 hours apart from drugs that are known to interfere with its absorption (see PRECAUTIONS – Drug Interactions).
The adequacy of therapy is determined by periodic assessment of appropriate laboratory tests and clinical evaluation.

The adrenal also receives innervation from the autonomous nervous system via the splanchnic nerve. This connection has been shown to transmit light information from the SCN directly to the adrenal gland and is responsible for modulating the adrenal sensitivity to ACTH46,47,48. Finally, it has been demonstrated that the adrenal cortex expresses a functional circadian clock, which gates the organ’s sensitivity to ACTH and further contributes to the generation of a robust GC rhythm10,49.

Stop biotin and biotin-containing supplements for at least 2 days before assessing TSH and/or T4 levels see DRUG INTERACTIONS. Do not administer in foods that decrease absorption of SYNTHROID, such as soybean-based infant formula see DRUG INTERACTIONS. Many drugs can inhibit Synthroid’s adsorption by the body; other medications may increase or decrease its effectiveness once it is adsorbed. Providing a complete list of medications to the doctor will help with getting the correct dose established for each individual patient. The «optimal dose» was determined for each patient as that dosage of thyroxine being taken when the thyrotropin-releasing hormone (TRH) response was normal (ie, an increase in TSH of between 4.7 and 25 mIU/L).

NP Thyroid

A surge in LH is crucial for ovulation in females but is absent in males and after ovariectomy72,73. Testosterone is predominantly produced in the testes, whereas estrogen and progesterone are predominantly synthesized in the ovaries74. These hormones act on multiple sites in the circadian system, modifying processes at the cellular and molecular levels. Sex differences in circadian regulation include the localization of sex hormone receptors in the SCN and daily secretion rhythms70,75,76. These hormonal variations also influence the HPA axis, contributing to sex-specific differences in stress responses across the day79.

However, if the serum TSH has not risen to greater than 20 mU/L, levothyroxine treatment should be discontinued for another 30-day trial period followed by oxyelite synthroid repeat serum T4 and TSH testing. Although thyroid hormones are excreted only minimally in human milk, caution should be exercised when SYNTHROID is administered to a nursing woman. However, adequate replacement doses of levothyroxine are generally needed to maintain normal lactation. Animal studies have not been performed to evaluate the carcinogenic potential, mutagenic potential or effects on fertility of levothyroxine.