Do you know the 5 points to pay attention to this kind of medicine commonly used in thyroid disease?

*Only for medical professionals to read for reference.
Rational use of levothyroxine sodium tablets In recent years, the prevalence of thyroid diseases has been on the rise, and the incidence of women is significantly higher than that of men
.

Patients with hypothyroidism (hypothyroidism) and patients after thyroidectomy usually need to take levothyroxine for life as a replacement therapy
.

To use levothyroxine sodium tablets rationally, you need to know at least these 5 points
.

1.
Understand the single pituitary gland to synthesize and secrete thyroid stimulating hormone (TSH), TSH stimulates the thyroid to synthesize and secrete thyroid hormones (T4, T3); T3 and T4 can feedback inhibit the synthesis and secretion of TSH
.

Small changes in T4 and T3 can cause large changes in TSH
.

TSH is a more sensitive indicator of thyroid function
.

TSH↑+FT4↓ can be diagnosed as hypothyroidism, TSH↑+FT4 is normal and can be diagnosed as hypothyroidism
.

Therefore, the dose of levothyroxine needs to be adjusted according to the levels of TSH and FT4
.

2.
Why is it not recommended to use liothyronine? The affinity of T3 and thyroid hormone receptor is 10 times that of T4.
Thyroid hormone mainly exerts its effect through T3, and T4 has no physiological activity under normal circumstances
.

Levothyroxine is synthetic T4, and liothyronine is synthetic T3.
Why is it not recommended to use liothyronine? First, T4 can be converted to T3.
Normal human thyroid secretes about 85μg of T4 and 6.
5μg of T3 every day
.

In the blood circulation, 80% of T3 is transformed from T4, and only 20% of T3 is directly secreted by the thyroid
.

——The replacement dose for adult patients with hypothyroidism is 50~200μg per day, with an average of 125μg per day
.

Second, T4 has a longer half-life.
Levothyroxine (T4) has a half-life of about 7 days, which can be converted into T3 in the blood "on demand", and the concentration of T3 is more stable
.

The half-life of liothyronine (T3) is about 0.
75 days, and the concentration of T3 in the blood fluctuates greatly
.

Liothyronine has fast action and short duration, and is more suitable for the rescue of mucinous edema coma
.