The
thyroid gland is a butterfly shaped gland that partially surrounds the wind
pipe and is under control of the hypothalamus and the pituitary gland in the brain. When thyroid function is not sufficient to meet, the
body’s needs it is called hypothyroidism.
Thyroid-stimulating hormone (TSH) is produced by
the pituitary gland at the base of the brain and tells the thyroid gland to
produce more hormones when needed. Elevated TSH levels can be a sign that the
thyroid gland is underactive.
Hypothyroid in female:
50 to 70% of hypothyroid female patients have
menstrual abnormalities. The most common manifestation is oligomenorrhea
(scanty bleeding during cycle). Severe hypothyroidism is commonly associated
with failure of ovulation. Ovulation and conception can occur in mild
hypothyroidism. These pregnancies are, however, often associated with
abortions, stillbirths, or prematurity. The latter may be of greater clinical
importance in infertile women with unexplained infertility.
Women who have unexplained infertility were nearly
twice as likely to have higher levels of a hormone that stimulates the thyroid
gland than women who did not conceive due to known issues with their male
partner's sperm count.
Even mild thyroid dysfunction may
contribute to unexplained infertility:
Unexplained infertility occurs when couples are
unable to get pregnant despite months of trying and a medical evaluation shows
no reason for their infertility.
Women with unexplained infertility had
significantly higher TSH levels than women with infertility due to a known
cause. Nearly twice as many women with unexplained infertility had a TSH
greater than 2.5 mlU/L compared to women whose partners had male factor
infertility. Although this is within normal range it may contribute towards
infertility.
Hypothyroid
can be due to autoimmunity:
Hypothyroidism influences ovarian
function by decreasing levels of sex-hormone-binding globulin and increasing
the secretion of prolactin. Prevalence of thyroid autoimmunity is significantly higher
among infertile women than among fertile women, especially among those whose
infertility is caused by endometriosis or ovarian dysfunction.
Presence of thyroid autoimmunity
does not interfere with normal embryo implantation, but the risk of early miscarriage is substantially raised. Thyroid maternal under function, even when considered mild (or
subclinical), may be associated with an impairment of brain development of the
baby.
Correction
of hypothyroidism:
In women of reproductive age,
hypothyroidism can be reversed by thyroxine therapy to improve fertility and
avoid the need for use of assisted reproduction technologies.
Hypothyroid patients who
conceive after gonadotropin stimulation or with oral medications for ovulation
induction do not need additional thyroid supplementation compared with those
who conceive spontaneously.
During pregnancy, women's
thyroid physiology undergoes well-defined changes, including an approximate
doubling in thyroxine-binding globulin concentrations due to increases in
estradiol concentrations, as well as a 30 to 40 percent increase in plasma
volume. These changes result in a significant increase in the total thyroxine
pool, primarily during the first trimester. Women with hypothyroid may have to
take little higher dose of thyroid medicine during pregnancy.
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