HYPERPROLACTINEMIA IN ASSOCIATION WITH SUBCLINICAL HYPOTHYROIDISM

Hyperprolactinemia is the most prevalent endocrine disorder in hypothalamic- pituitary axis (1). Pathologic hyperprolactinemia is generally applied for the situation in which prolactin level increases because of some reasons other than physiologic causes. Prolactin secretion is controlled by prolactin inhibitor factor that is secreted from hypothalamus, other factors like vaso active inhibitory peptide (VIP) and Thyroid relising hormone (TRH) cause to increase prolactin secretion (1). In fact, TRH in addition to increasing TSH causes to rise prolactin level (2). In patients with primary hypothyroidism, increased levels of TRH can cause to rise prolactin levels and these patients may have galactorrhea (3). Different increased level of serum prolactin has been reported in 30% of patients with primary hypothyroidism (4). Subclinical hypothyroidism is defined by high TSH and normal thyroid hormones (5). Although many studies had shown that this situation of thyroid never create a special symptom in people but most of the sub clinical hypothyroidism patients suffer from the symptoms of this disease like fatigue, musculoskeletal symptoms and cold intolerance (5). Some studies have reported musculoskeletal and cardiovascular metabolic disorders in subclinical hypothyroidism similar to primary hypothyroidism (6, 7). In 1988 for the first time, an increase of serum prolactin was reported in a woman with carpal tunnel syndrome and subclinical hypothyroidism (8). After that, one study showed the relationship between subclinical hypothyroidism, hyperprolactinemia and sterility (9). Although some studies reported that hyperprolactinemia is rare disorder in subclinical hypothyroidism (10). Considering the clinical importance of hyperprolactinemia in ovulation disorders (11), sterility (12, 13) and menstruation disorders (14, 15), this study was done for the determination of hyperprolactinemia prevalence in subclinical hypothyroidism patients and clinical related symptoms in subclinical hypothyroidism patients in Sari , Iran.