Relationship of thyroid blood flow to reproductive events in normal Chinese females

Thyroid volume and Doppler evaluation of inferior thyroid artery in ultrasound: Comparison between current and previous users of oral contraceptives

BACKGROUND

This study aimed to compare thyroid volume and Doppler sonographic evaluation of the inferior thyroid artery using ultrasound in current and previous users of oral contraceptives (OCs).

METHODS

We evaluated 119 women who either currently use (n = 66) or have previously used OCs (n = 53) using color Doppler ultrasound for thyroid volume and resistance index, peak-systolic, and end-diastolic velocities of the inferior thyroid artery. Previous OC users were divided into two groups: previous OC use for <1 year and previous OC use for ≥1 year.

RESULTS

A comparison of the thyroid volume revealed an increased volume in women with previous OC use for ≥1 year and in current users compared with those with previous OC use for <1 year (previous OC use for ≥1 year: 7.49 mL versus previous OC use for <1 year: 6.13 mL; p < 0.01). The relationship between OC use and an enlarged thyroid remained after adjusting for thyroid-stimulating hormone levels (p = 0.03). There were no differences in the inferior thyroid artery blood flow measurements.

CONCLUSIONS

In healthy women, current use and previous OC use for ≥1 year were associated with increased thyroid volume that was unrelated to increased blood flow in the gland.

Ultrasonographic assessment of the thyroid gland and adjacent anatomic structures in Indo-Pacific bottlenose dolphins (Tursiops aduncus)

OBJECTIVE

To evaluate the use of ultrasonography for thyroid gland assessment in healthy Indo-Pacific bottlenose dolphins (Tursiops aduncus), describe the ultrasonographic appearance of the thyroid gland and adjacent anatomic structures, and identify potential associations between variations in thyroid gland morphology and demographic features in this species.

ANIMALS

18 captive Indo-Pacific bottlenose dolphins.

PROCEDURES

1,404 ultrasonographic examinations of the thyroid gland and adjacent anatomic structures (eg, cervical lymph nodes, musculature, and vasculature) were performed during the > 3-year study period. Shape, echogenicity, and homogeneity of thyroid glands were assessed, and glands were categorized into morphological configurations on the basis of results of 2-D and 3-D ultrasonographic evaluation. Associations between demographic factors and thyroid gland morphology were assessed.

RESULTS

Thyroid lobes appeared elliptical or fusiform in the transverse scan plane and round to oval in longitudinal scan planes; morphologically, glands comprised 2 lobes joined by an isthmus or a roughly diamond-shaped structure located on the ventral surface of the trachea. Major blood vessels and cervical lymph nodes were identified. Thyroid parenchyma was typically uniform and homogeneous, with echogenic reticulations and well-defined borders. Thyroid glands were hypoechoic or isoechoic relative to the sternocephalicus muscle; echogenicity was greater in adolescents than in adults. Thyroid gland volume differed between sexes, between sexually mature and immature dolphins, and among age groups and was positively correlated with body length and weight.

CONCLUSIONS AND CLINICAL RELEVANCE

Ultrasonography provided a reliable and repeatable method for evaluation of thyroid glands and adjacent anatomic structures in live dolphins.

Evaluation of the thyroid blood flow with Doppler ultrasonography in healthy school-aged children

OBJECTIVE

To determine the relationship between thyroid blood flow and anthropometric measurements, pubertal stage, and thyroid and gonadotropic hormones.

MATERIALS AND METHODS

We examined 123 healthy school-aged children prospectively (69 boys (56.1%) and 54 girls (43.9%), 7-17 years old). Their sex, age, body weight, height, body mass index (BMI), and pubertal stage were determined. Serum thyrotropin, free thyroxine, luteinizing hormone, and follicle stimulating hormone were measured in both genders, along with testosterone in boys and estradiol in girls. The peak systolic velocity (PSV), resistance index (RI), and pulsatility index (PI) of the superior thyroid artery were determined. The correlations between the Doppler parameters and these factors were investigated.

RESULTS

There were no differences in age, weight, height, BMI, thyroid volume, PSV, RI, or PI between boys and girls (P>0.05). The PSV and PI showed strong correlations with age, height, weight, puberty stage, thyroid volume, and BMI. The RI showed a strong inverse correlation with age, height, weight, puberty stage, and thyroid volume and a weak inverse correlation with the BMI.

CONCLUSION

Determination of the thyroid arterial flow in normal healthy children is important during a Doppler ultrasound (US) examination. Doppler US parameters and their percentiles should be described in healthy children from different age groups, and these percentiles will aid in interpreting Doppler US in children.

Assessment of variability of renal blood flow Doppler parameters during the menstrual cycle in women

OBJECTIVE

To estimate variability of renal flow Doppler parameters during the menstrual cycle in young women, and to explore whether the parameters oscillate substantially throughout the cycle.

METHODS

The peak systolic, mean, and end-diastolic velocities, pulsatility (PI) and resistance (RI) indices, acceleration time (AT) and index (AI) of the right renal artery were measured nine times during the cycle with duplex sonography in 14 healthy women (age range, 23-25 years), and correlated with plasma concentrations of 17beta-estradiol and progesterone. Coefficient of variation (CV), interclass correlation (rho), and repeatability coefficients (RC) were used to measure the variability.

RESULTS

The measures of the variability for AI and AT were: CV = 45.4% and 37.3%; rho = 0.25 and 0.15; RC = 10.1 and 99.5, respectively. The CV for flow velocities varied from 24.1% to 25.5%, rho from 0.49 to 0.50, RC from 22.7 for end-diastolic to 63.3 for peak systolic velocity. The respective figures for PI and RI were: CV = 17% and 8.3%; rho = 0.21 and 0.29; RC = 0.53 and 0.15. Fluctuations of the flow parameters, hematocrit, hemoglobin, heart rate, and systolic blood pressure during the menstrual cycle were insignificant, while the diastolic blood pressure decreased by about 7 mmHg (P < 0.01) in the luteal phase.

CONCLUSION

The variability of renal flow Doppler parameters during the menstrual cycle in young healthy women is substantial. However, fluctuations of the values of the parameters throughout the cycle were non-significant.

Thyroid dysfunction and women's reproductive health

Thyroid dysfunction is extremely common in women and has unique consequences related to menstrual cyclicity and reproduction. Even minimal hypothyroidism can increase rates of miscarriage and fetal death and may also have adverse effects on later cognitive development of the offspring. Hyperthyroidism during pregnancy may also have adverse consequences. Accordingly, thyrotropin (TSH) determination is warranted for all women planning pregnancy or those already pregnant. Replacement doses should be carefully monitored throughout pregnancy because the increased renal iodine loss and estrogen-induced rise in thyroxine-binding globulin (TBG) often result in a higher dose requirement. Although thyroid abnormalities are part of the standard differential diagnosis of menstrual disorders, recent studies indicate that these are relatively infrequent causes. Nonetheless, TSH is still required as part of the laboratory evaluation of women with abnormal cycles. The incidence of postpartum thyroiditis is high--6%-8% in various studies. A TSH should be performed in all postpartum patients who are depressed, who complain of unusual fatigue or anxiety or have any of the classical symptoms of hyperthyroidism or hypothyroidism. Practitioners providing health care for women should be alert to thyroid disorders as possible etiological factors in nonspecific symptoms such as fatigue and depression. However, most women with these symptoms are euthyroid; replacement therapy for them is not indicated. The long-standing dogma of thyroidology that replacement with levothyroxine alone is satisfactory for all hypothyroid patients has recently been questioned but results of trials are inconclusive. Nonetheless, satisfactory regimens can be found for the vast majority of patients.