Increase in Thyrotropin Is Associated with an Increase in Serum Prolactin in Euthyroid Subjects and Patients with Subclinical Hypothyroidism

Abstract

Background: Prevalence and clinical significance of hyperprolactinemia in subclinical hypothyroidism have been reported in few studies. The upper limit of the normal range for TSH used to diagnose subclinical hypothyroidism is a matter of controversy. Some experts believe that the upper limit of the normal TSH range should be reduced from 4.2 to 2.5 mIU/L. Some evidence suggests a positive relationship between TSH > 2.5 mIU/L and cortisol as an indicator of metabolic stress. With this view prolactin as a stress hormone can be elevated in TSH >2.5 in comparison to TSH< 2.5. Hence the aim of this study was to evaluate the relationship between TSH and prolactin levels in the TSH range <10. Methods: This cross-sectional study was performed on apparently healthy subjects with TSH<10 mIU/L. Subjects with the age of 18 to 35 years were enrolled. The sera were analyzed for prolactin, FT3, FT4, TSH, TPO-Ab and Tg-Ab. Results: From the total number of 519 participants, in 65 subjects (12.5%) TSH was < 2.5. Seventy-nine subjects (15.2%) had TSH: 2.5-4.2 and 375 (72.3%) of the participants had TSH> 4.2 mIU/L. The mean age, weight and BMI of subjects in the three TSH groups were not significantly different. In the three TSH groups, the prevalence of hyperprolactinemia was zero, 3.8 and 30.7%, respectively. There was a positive and significant correlation between prolactin and TSH levels (r=0.613). Conclusion: Hyperprolactinemia is common in patients with subclinical hypothyroidism (30.7%) and there is a positive correlation between TSH and PRL in subjects with TSH<10 mIU/l.

Effect of TSH on oocyte maturation of PCOS patients with normal thyroid function in IVF

“…When TSH level is abnormal, it will affect hypothalamus function, resulting in abnormal hypothalamus pituitary gonad axis function [5][6][7]. Some studies have shown that the majority of female patients with thyroid dysfunction have symptoms such as irregular menstrual cycle, rare menstruation, irregular uterine bleeding, and some of them have polycystic ovarian changes with abnormal blood glucose metabolism and lipid metabolism disorder [19][20][21], which are considered to be related to insulin resistance and islet cell damage. At the same time, the imbalance of gonadal axis in PCOS patients may affect the pituitary thyroid axis.…”

Pars Distalis and Pars Tuberalis Thyroid-Stimulating Hormones and Their Roles in Macro-Thyroid-Stimulating Hormone Formation

“…There was also a high frequency of patients with hyperprolactinemia (21% and 46%) with autoimmune thyroid disorders [95,96]. The reverse correlation, hyperprolactinemia in patients with SCH, was reported, with a prevalence of 8-34.93% [94,97].…”

“…Macro-PRL, which is more common than macro-TSH, was reported to have neither a specific physiological nor a pathological role [93]. Increased TSH levels in patients with hyperprolactinemia suggest a common tendency for the formation of antihormone antibodies [94]. Since 72.3% of patients with hyperprolactinemia had TSH levels in the upper range (>4.2 mIU/L), it may be hypothesized that macro-TSH was present in the samples due to the cross-reactivity of anti-PRL antibodies [94].…”

“…Increased TSH levels in patients with hyperprolactinemia suggest a common tendency for the formation of antihormone antibodies [94]. Since 72.3% of patients with hyperprolactinemia had TSH levels in the upper range (>4.2 mIU/L), it may be hypothesized that macro-TSH was present in the samples due to the cross-reactivity of anti-PRL antibodies [94]. There was also a high frequency of patients with hyperprolactinemia (21% and 46%) with autoimmune thyroid disorders [95,96].…”